That's not part of the inner drum. It's a separate cover piece that snaps to the top of the outer tub.

That kind of damage typically happens if a large item such a comforter is too big to fit and rubs on the tub cover during spin ... or a similar overload happens with regular clothes. Any possibility of that having happened?

Could also be that the tub cover is broken/loose and rubbing on the rim of the inner drum .... or the drum, drive shaft, or tub is askew causing the same effect. Is any of that evident if you rotate the drum by hand? Does it rub on the tub cover?