Seems to be pcgs favorite bust half grade lately. I've had a ton come back at 45 too. Some I thought 40 some I thought 50 and the rest I agree with
Given how difficult it is to get a CAC sticker on an AU50, maybe AU53 is the new 50? The one I posted here yesterday is a CAC'ed 45.
I've always thought 53 to be a "copout grade" similar to 58 - in many cases, the TPG's just don't want to exert the time and effort to factor strike, die state and external influences into the quality of the coin they're looking at. Not that those honest grades don't exist, just that too many examples deserve other/better grades.
The glass is half empty, or half full, and only your viewpoint differs. Me, I'm a pragmatist and see only that I need to drain it and get a refill.