Even if the manager specifically says "Hey everyone, give me some feedback. Be open and honest" - That's a trap. No one will ever actually do that, because if you bruise your manager's ego, they have the power to make your life a living hell.
As someone who has worked with managers who did tried to get too involved in projects, they just become a dictator. Since the manager will play an oversight role in the project, any small issues will be visible to them at all times. Normally, the team could work out small roadblocks on their own to keep stress low. If the manager is involved, they'll often try to "make themselves useful" and slow things down. Let's not even mention manager statements like "Hey guys, let's keep a note of this so we can work on restructuring our processes in case this happens in the future"... (Because everyone loves redrafting SOPs every 2 months, right?).
A good manager is one that stays out of the way and lets you do your job. Having a manager on a project kinda feels like that episode of The Office when Michael comes to Jim's party and everyone was just kinda standing around awkwardly.
1) I pick what I'm going to work on after the rest of the team picks their tickets.
2) I fix one bug per day, not matter what.
3) HIPPO (HIghest Paid Person's Opinion) is not an acceptable reason to make a decision.
It's worked well for me, your milage may vary.
Then I'll never know how to make things better. It's dysfunctional when you can't communicate safely and equally dysfunctional when problems are hidden for fear of a manager's ego.
If you cross the barrier the people in your team will be put under pressure having to do things like for example disagreeing with technical decision or debating something in a code review with... the same person that has the power to promote or fire them.
It creates a power gradient in every day activities.
That's "stealth" micromanagement regardless of the good intentions and technical skills of the manager.