Huh. I had this happen to my M1 within a month of buying it. I was totally mystified as I woke up in the morning and it had been sitting on some thick carpet over night and suddenly there was a crack in it. I took it in and they said I must have caused the damage. I still haven't repaired it for months, as it was quite expensive and I was just assigned a new work laptop and was strapped for cash.

I've had plenty of Macbooks before that have taken a lot of abuse, but this was just bizarre.