The main problem with using dice is knowing that the eventual seed was indeed generated from those dice. For example, ColdCard runs the dice input through SHA256 to produce the seed. But to confirm that this is what it’s actually doing, you need to send the same dice rolls to a second implementation to confirm that it produces the same BIP-39 seed.

To avoid this, one would need to use a dice-to-BIP-39 encoding scheme that can be performed by hand, offline.