I think you're confusing two things. A chatbot keeps talking because it creates engagement and just saying "i dont know" or "no" kills the engagement so naturally one would assume it is trained to always try to provide some sort of an answer and try to keep the user engaged.
But that doesn't mean it will do whatever you ask it. Ask Chatgpt to assisinate someone or buy drugs and it will tell you to f off. But what corrupts people, is these kind of things, where you are a mini king beyond ethics and morals.
Thats a different kind of "inablity to say no".
Chatbots say "no" or "I don't know" all the time, so once again I feel like the anti-AI crew don't actually use it.
I think that it depends on which bot, and how they are set up.
It's been a while, but I remember changing a setting on mine, so it is less sycophantic.
Mine says "I don't know," frequently, and also suggests against ideas.
But it also confidently states complete garbage, much more frequently. I have to stay on my toes.
I suspect that you're correct, but the end result is the same.