> Or is it literally that the freezing and thawing can't happen evenly when you're too big?

This. You literally can’t evaporate all the thawing agent out of the blood of the organism without substantial burns by sheer volume

Hmm I wonder if some kind of beamforming would work? I think that's what the Miele Dialog uses to enable you to cook a fish while it remains in a frozen block of ice

https://www.miele.ie/c/revolutionary-excellence-1425.htm

That's really interesting, thank you - do you know how this was done, like in a practical sense?