How is this not a blunder?
No. No. no, no. It was not the engine that said that. The engine does not use such terms, only numbers.
Chess.com has a script that labels moves with those weird adjectives. That script notably has difficulty with those labels when the position is totally winning or totally losing for someone.
In this case, black is obviously totally winning no matter what. White's blunders speeds up the matter, but is that important? White is completely lost anyway.
Yes, you can say that it is a bug, and I agree. Chess.com's programmers will probably argue that it isn't.