This is the same as our approach. Boot from attached storage, then remove the storage device to show the system is probably running from RAM. SeedSigner is just a single purpose, hardened, verifiably offline computer.
Discussion
Love this approach, and I am a fan of SS.
Have yall given an expert cold eyes review further consideration?
https://github.com/SeedSigner/seedsigner/issues/391#issuecomment-1599256650