[SpicyLemonZest]

I haven't reviewed it myself, but when a mathematician calls a proof "quite poor" and experts have to "sift through" it, I would understand that to mean that it's technically incorrect. Errors like "This statement isn't correct, but it points towards a weaker statement that is, and the subsequent steps can be rebuilt on top of the weaker statement" are pretty common in output from both LLMs and math students.

[BeetleB]

No - It likely means that the proof was meandering, and had lots of additional pointless steps.

[estimator7292]

Good/bad is orthogonal to correct/incorrect.