I've gotten my Apple Silicon Case Warranty replaced by the Apple Store. It can be done as long as the defect isn't the result of a drop or some super obvious mutilation to the case.
The only nit was that Apple Store can't grab a case off the shelf and just give it to you. I had to go in, show the case to them, they agree to Warranty it. Then Apple puts in a request for a replacement case (from a different stock pile). I had to come back maybe a week later and get my replacement (kept the old one until then). I think I had to turn in the old case, too.