I bought three one for each member of the family.
Each of the buttons fit differently. One is sunken below the surface by approx 2pm. One is raised slightly above, perhaps 1mm. Finally the third one is off center in the opening.
It's no big deal. We have to collapse our expectations, since Apples quality is bound to degrade & suffer due to outrageous demand placed on foxconn workers to build these at warp speed to meet demand.
The three all work ok, not great, but ok, and they should last a year which is all I care. I'll buy new ones next years anyway. The days of the long lasting Apple product are over. These are throwaways in the new era.
For those who manage to get more time from theirs, consider yourself lucky. Besides I've noticed there's plenty of you tube videos to teach you how to repair these rather cheap ill fitting buttons.
The good new is, perhaps Apple will employ contemporary thinking and acquiesce. Installing touch a sensitive button makes complete sense, it's easy since the display is touch sensitive and you don't see those failing.
Sometimes common sense and the obvious escapes companies like Apple.