Nah, there's no reason a professional should ever need to ask. It doesn't become malicious just at the point of asking, though it's not ever necessary. A T asking questions like that makes more sense when it's directly relevant to an issue you brought up yourself, and makes much less sense when you end up asking yourself why they asked.

I'm thinking that with therapists, a good rule is that if you're questioning their behavior in the first place, then chances are it actually is questionable.

T's fundamentally really shouldn't ever be "volunteering" anything. Not information, not interventions, not suggestions, nothing. They should always just be responding to, adding to, aiding with, or otherwise commenting on the things that you personally are bringing up. They should not be the one setting the topic or the agenda, or lecturing, or teaching, or preaching, or prying.

Nobody's perfect but, that's more or less the standard that they really should be held to. It takes a lot of maturity and self-control to truly fill those shoes.