NB I start by talking about type theory in this first section, but the second section contains comments about usual first-order logic and Heyting arithmetic that also make sense on their own.
When we ask about the constructivity of certain moves, Per Martin-Löf's type theory provides a fairly comprehensive philosophical framework and a useful starting point, in the sense that almost all stakeholders accept it as constructive.
And we can formulate MLTT in such a way that explosion occurs as a proper theorem, not an axiom.
In type theory, as in most foundational systems, the statement $0=1$ is naturally explosive, in the sense that you can prove anything using $0=1$ without ever invoking any rule akin to explosion ($\bot$-elimination). How?
Let us start with MLTT and let $\mathcal{U}$ denote the type of small types (we won't need a cumulative universe hierarchy). Consider the modified type theory MLTT' obtained by removing the built-in empty type from MLTT. I.e. we only have dependent sum and product types $\Sigma,\Pi$, equality types $=$ on all sets, the type of natural numbers $\mathbb{N}$, and (if you wish) the singleton type $\top$, with their usual introduction and elimination rules. We define all other types using these primitives.
I will now show that the statement $0=1$ is naturally explosive in the modified type theory MLTT', i.e. that $0 = 1 \rightarrow P$ for any proposition/type $P$.
Assume $0 = 1$ and take your favorite proposition $P : \mathcal{U}$.
We can use the induction principle on the natural numbers (the elimination rule for $\mathbb{N}$) to construct a function $f: \mathbb{N} \rightarrow \mathcal{U}$ so that $f(0)$ reduces to $\top$, but $f(n+1)$ reduces to $P$ for all $n:\mathbb{N}$.
We can prove the congruence rule, $a = b \rightarrow f(a) = f(b)$ by applying the usual introduction and elimination rules of equality. Applying the congruence rule to the equality $0 = 1$, we get $f(0) = f(1)$, which reduces to $\top = P$.
Moreover, if $\top = P$, then $\top \rightarrow P$ holds. Why? Because we can obtain $\top = P \rightarrow (\top \rightarrow \top) \rightarrow (\top \rightarrow P)$ from the elimination rule for equality, and you can prove $\top \rightarrow \top$ itself trivially.
So if $0 = 1$, then $\top \rightarrow P$. But $\top$ holds, so by modus ponens (the elimination rule for dependent product), we immediately get $P$. Therefore, we have shown that $0 = 1 \rightarrow P$ as claimed.
At this point, we're done. We can just introduce $\bot$ as an abbreviation for $0=1$, and define negation $\neg P$ as $P \rightarrow \bot$ as we'd normally do, and go on with our lives. We regard explosion as constructive because we all agree on the constructivity of MLTT (at least when formulated without $\bot$, and hence without explosion), and we can explicitly define $\bot$ as $0=1$ and prove it explosive inside this constructive theory.
Of course, one could worry about the anachronistic character of the story above, in that intuitionistic logicians accepted explosion decades before Martin-Löf formulated his type theory in 1971.
But a similar phenomenon occurs even in foundational theories formulated in ordinary first-order intuitionistic logic: e.g. $0=1$ is explosive in Peano Arithmetic in Minimal Logic (PAML, the first-order Peano axioms stated in minimal logic -- not to be confused with minimal arithmetic, which most people use as a synonym Robinson's Q).
For example, if you want to prove using $0=1$ that every number is even in PAML, you can just multiply both sides of the inconsistent equality by $2$ to get $0=2$, apply transitivity to get $1=2$, then replace $1$ with $2$ in $\forall x. 1\cdot x=x$ to conclude $\forall x. 2\cdot x=x$, and then a fortiori $\forall x. \exists y. 2y = x$. You can do this systematically, by induction on the structure of the target formula $P$ to prove that $0=1 \rightarrow P$ for any proposition $P$ in the language of PAML.
This all relies on one key insight. The rules of the connectives determine their meaning. And $\bot$ does not have any other rules apart from its elimination rule (ex falso). Without rules, it does not, and cannot, have intrinsic meaning: it simply denotes "some formula". This happens in minimal logic: in minimal logic you can prove $A \rightarrow \bot$ precisely if you can prove $A^{[\bot/B]} \rightarrow B$ for any formula $B$, where $[\bot/B]$ denotes replacing all occurrences of the symbol $\bot$ with the formula $B$. In minimal logic, $\bot$ really just denotes some arbitrary formula.
When we add an elimination rule for $\bot$, we declare: we don't want this symbol to stand for any arbitrary formula. Instead, we want it to stand for some explosive formula. We don't really care which one, they're all logically equivalent anyway. But we're not adding anything new: we already know that explosive formulas exist, e.g. $\bot$ could stand for $0=1$.
And that is why we consider explosion constructive.
I had a conversation on this exact topic with four other constructive mathematicians at CM:FP '23 earlier today. I'm quite amused to see the question come up here a few hours after that. It must be on everyone's minds.