>>> 'Real timeshift' would be be something like ZFS snapshots, which we still don't have in Linux because of dogma.
Nothing stops you from installing ZFS, it is fully supported since 16.04 was released.
May be dogma, who knows.
What the dogma prevents is from distributing kernels with ZFS built in, this is by default you can't boot of a ZFS partition, but this is hardly a problem when you can modify your initram to have the ZFS loaded on boot from the classic /boot formatted as EXT4.
ZFS in Linux is very well supported these days.