It's a continuum with bigger, denser, and otherwise harder to consistently rewarm and perfuse ramping the difficulty up, likely on a non-linear scale.

We may well see cryonically frozen lab rats fully resuscitated in the coming years (likely still with lots of complications at first), but we should contain our optimism given there's probably at least at much of a gap between cycling an embryo or tardigrade and cycling a rat as there will be between cycling a rat and cycling a human. We have notoriously hungry brains!