Squeaking/screeching sound when AC stops

That's the squirrel part of the squirrel cage. He's gasping for breath.

Does sound like it’s blower motor unit related - loose bolt in blower housing, squirrel cage blower wheel making contact with housing at low rpm when stopping, … the way you describe it doesn’t sound like the motor itself, though I guess it could be - most blower motors, particularly a fairly new unit, I would think would have oiless/self lubricated bearings/bushings.

I wouldn’t let it go very long like that. If you need a tech, major parts should be covered under warranty, but labor would be billable assuming you had a 1 year labor warranty which is pretty standard.