Well, I thought I already described what seemed to me to be a charitable and reasonable take on it.
"I put as much effort in as can reasonably be expected; I tried to evaluate it fairly; but the documentation and supporting code is so bad that I may have made mistakes. If so, blame them for making it impossible to evaluate fairly, not me for falling over their tripwires."
If something is badly documented and badly implemented, then I think it's OK to say "I think this is badly designed" even if you found it incomprehensible enough that you aren't completely certain that some of what looks like bad design is actually bad explanation.
If some of the faults you think you see are in fact "only" bad documentation, then in some sense you're "spreading FUD". But after putting in a certain amount of effort, I think it's reasonable to say: I've tried to understand it, I've done my best, and they've made that unreasonably difficult; any mistakes in my account of what they did are their fault, not mine.
(I should reiterate that I haven't myself looked at the AT protocol or Bluesky's code or anything, and I don't know how much effort SW actually put in or how skilled SW actually is. It is consistent with what I know for SW to be just maliciously or incompetently spreading FUD, and I am not saying that that would be OK. Only that what SW is admitting to -- making a reasonable best effort, and possibly getting things wrong because the protocol is badly documented -- is not a bad thing even when described with the words "I don't care if I'm spreading FUD".)
