My take is that this is good (for me). At least the body can sink.
If you don't sink evenly, your spine is aligned though not level. Whereas in a traditional mattress a poor fit to your body will feel like a hammock, or a hard floor with pressure points
I’ve never seen any evidence to suggest this was good for spinal alignment. If you’re a side sleeper, it can also be bad for your shoulders if it doesn’t sink in enough.