Do the errata changes to "your <class> spells" prevent coffeelock cheese?

Question

The errata introduced changes to specify spell slots' classes. I was wondering if those changes could somehow prevent coffeelock cheese in the spirit of this Jeremy Crawford tweet to interpret class features as reserved for that specific class?

Quote from the tweet:

DMs, if you allow multiclassing in your game and someone is tempted to abuse the combination of Flexible Casting and Pact Magic, remember this: one way to read the multiclass rules is that your Pact Magic slots are useless for any non-warlock thing besides casting spells.

---

Coffeelock Exploit

Coffeelock is a sorc/warlock multiclass that exploits these mechanics:

Flexible Casting

You can use your sorcery points to gain additional Spell Slots, or sacrifice Spell Slots to gain additional sorcery points. You learn other ways to use your sorcery points as you reach higher levels.

Pact Magic Spell Slots

You regain all expended spell slots when you finish a short or Long Rest.

The "coffeelock" character uses flexible casting to convert warlock spell slots into sorcery points then turn those sorcery points into spell slots, short-resting to recover warlock spells slots then turn those into more sorcery points, virtually giving that character unlimited spell slots so long as the character does not take a long rest.

---

The Errata (As of April 2020)

Changes were made to Spell Slots in D&D 5E's Players Handbook to specify that spell slots now belong to a class. Changes emphasized below in bold italics:

Spell Slots (Sorcerer)

The Sorcerer table shows how many spell slots you have to cast your sorcerer spells of 1st Level and higher. To cast one of these sorcerer spells, you must expend a slot of the spell's level or higher. You regain all expended spell slots when you finish a long rest.

Spell Slots (Warlock)

The Warlock table shows how many spell slots you have to cast your warlock spells of 1st through 5th level. The table also shows what the level of those slots is; all of your spell slots are the same level. To cast one of your warlock spells of 1st Level or higher, you must expend a spell slot. You regain all expended spell slots when you finish a short or long rest.

---

Main Question

Ignoring sleep mechanics and Jeremy Crawford's tweet, I wish to know if these errata changes could be interpreted in a clear way that prevents the "coffeelock" exploit?

Secondary Question

In what way do these changes actually impact the game?

---

A positive answer to my main question, if it exists, will help in Adventurers League and Rules-As-Written sessions without having coffeelock arguments sprawl over to sleep mechanics and sage-advice territory. This will keep rulings concise and efficient.

Answer 1

No, your discretion as a DM prevents it.

Spelling out that you can cast "sorcerer spells" or "warlock spells" with your spell slots doesn't affect this exploit, because the exploit isn't about whether you can cast spells; it's about whether you can feed them into Flexible Casting to get Sorcery Points.

The most important rules governing this whole issue are the ones in the Multiclassing section about how to reconcile spellcasting from multiple classes:

Spell Slots. You determine your available spell slots by adding together all your levels in the bard, cleric, druid, sorcerer, and wizard classes, and half your levels (rounded down) in the paladin and ranger classes. Use this total to determine your spell slots by consulting the Multiclass Spellcaster table.

Pact Magic. If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.

So, the change to the the Pact Magic feature to say that these spell slots are for casting "warlock spells" doesn't even restrict them to casting warlock spells. If you have any other spellcasting class, you explicitly can use warlock spell slots to cast that class's spells and vice versa.

But that's only for casting spells. Breaking down a spell slot into Sorcery Points isn't casting a spell. (Neither is, say, Divine Smite.) So there's no rule, before or after the errata, saying that you can or can't use Pact Magic spell slots for this purpose. So make a ruling based on what's good for your group.

This still applies in AL, by the way. The DM is still empowered to interpret the rules in edge cases such as this; they're just not supposed to change the rules.

As an Adventurers League Dungeon Master, you are empowered to adjudicate the rules as presented by the official materials (PHB, DMG, MM, etc.). Run the game according to those rules, but you are the final arbiter of any ambiguities that might arise in doing so.

But doesn't Flexible Casting just say "spell slots"?

You can use your sorcery points to gain additional spell slots, or sacrifice spell slots to gain additional sorcery points.

Well, yes. But so does Pact Magic:

You regain all expended spell slots when you finish a short or long rest.

If we ignore the context--that these features belong to separate classes and are referring to spell slots obtained from different sources--then this trick with Flexible Casting isn't even needed. Your Sorc 9 / Warlock 1 can burn all their spell slots and then take a short rest and get them all back. Hey, it says "all expended spell slots", right?

This is absurd and nobody plays this way.

The multiclassing rules very clearly distinguish spell slots you gain from Spellcasting classes from Pact Magic spell slots. They are interchangeable for the specific purpose of casting spells that you know from any of your spellcaster classes.