I agree 100% with you, Leor.
I thought about that when writing the article. There's a blurred line between what I say and the cases you point out here. I'd say the threshold lies in whether we all are either using the systems (e.g. Grammarly) or aware of their use (e.g. google suggestions).
You're right AI is everywhere and it will be. I'm actually not criticizing using AI to write (that's another conversation). I'm criticizing people that would profit from others not knowing whether someone is using it or not.
Until it's commonplace to use AI systems (or their use is democratically distributed - to the extent that it is possible) I'd always disclose their use. I'd say the same about Grammarly if only a few tech-savvy knew about it or only a few privileged had access to it.
P.S. I've used Grammarly to edit this comment :)