Stacking mattress covers

I read on a post that you should cover your crib mattresses by mattress cover, sheet, mattress cover, sheet, mattress cover, and then again another sheet.

It is claimed that this will be super helpful in the nights of a blow out, or if baby throws up, you can just lift the sheet and mattress cover out and then it will already be set.

My only concern is, that the mattress is made a certain way for a reason, and it is meant to be somewhat stiff.

Wouldn’t layering it cause too much cushion? Or am I over thinking it?