Of course, the only way to know for sure what the creator meant is to ask them, and you may have some luck getting an answer from them on Instagram or Twitter.
That said, it seems that it could have easily been made clear in the feature text by instead writing:
if the check fails by 5 or more or succeeds, you also expend a spell slot of the spell's level.
It seems straightforward to us looking at it after-the-fact that if they had intended to have a successful check expend the spell slot, they could have easily written that in the feature description. So it isn’t apparent from what is actually written that a spell slot is expended on a successful check. But again, we don’t actually know what they meant, and they are still around and active on social media, so you might try asking them.
Regarding the comparison to the Coffeelock, the primary gamebreaking feature of Coffeelock is that it allowed for arbitrarily large stockpiling of slots. There was no hard cap on how many slots the Coffeelock could build up. This class, however, is given a hard limit:
You can maintain a number of active tokens equal to your proficiency bonus.
Your extra slots are explicitly limited by your proficiency bonus. So while it’s a strong feature, it’s really nothing like the Coffeelock.