At this point, someone should be periodically testing ChatGPT by scoring it against a set of questions (constant, not public, of varying difficulty, and enough that the score is consistent if you run the multiple times on the same day). If ChatGPT's score declines, there's clear evidence that OpenAI made it worse.

Otherwise, I really doubt any of these reports. "ChatGPT got worse" is so common that, if it was true, there'd be solid emperical evidence (there's the Stanford study, https://arxiv.org/pdf/2307.09009, which shows ChatGPT can degrade across releases, and I believe that; but these claims are about it degrading in the same release).