This is what I think: When OOM kills an app on a phone with 1GB RAM (when no such things would happen years ago on a phone with 256 RAM), then it is a big problem. I would rather have this problem solved with optimization, than hiding the problem by keeping its cover.
So yes, I would like to see this functionality reverted before final Sailfish UI 2.0 comes out - if an app crashes, then I want to see it and deal with the problem, not have it hidden like on Android and other non-multitasking operating systems.
EDIT: I understand that keeping its cover helps keeping other covers in their positions, but I think that this functionality can be easily misused as a mean to have Android-like "single-tasking".