I don’t believe that was unheard of. Even today, Americans are not uncommonly buried above ground in places where the water table is high, such as Louisiana, and some are buried in mausoleums in various states, including California.
And as the ‘Outlaw Josey Wales “ would say, Buzzards got to eat, same as worms!
I was just pointing out that Christ being “buried” doesn’t set a precedent to being buried underground.