Same here. I have also started to suspect the same. I have been monitoring one account for the last few weeks, and within this time, the account have posted 3/4 times only which seems like AI generated to me. I don't want to publicly post that until I'm sure that he is posting AI generated text.
This will be somewhat a disaster if someone with a long list of account starts to participate in signature campaign and post AI generated garbage, I'm pretty much sure we will see the day in the coming future.