Even worse, the software-based proofs are not the same as the plain text ones that they're giving out.

There's literally no reason to trust them, because it's completely divorced from the actual text.

Saying "self-verified" is massively downplaying it. They are formalized and checked in Lean4 1, which is a programming language used by mathematicians today, to mechanically check their proofs to rule out human error. In other words a theory being stated in Lean generally means it's more likely to be correct than one stated in mere human language.

Now, Lean, like any piece of software, has had bugs. A while back someone exploited a Lean bug to "prove" the Collatz conjecture 2. So it is possible that AI agents found a bug and used it. But the vibes I got from mathematicians in the field is that that's not very likely.