It turns out, that they'd made this discussion before: https://github.com/iancoleman/bip39/issues/435#issuecomment-1145503821

As far as I can tell, Coldcard does also use the SHA256 hash of the input, which is likely the dice rolls: https://github.com/Coldcard/firmware/blob/master/docs/rolls.py#L15.
Interested discussion to this StackExchange question as well: https://crypto.stackexchange.com/questions/10402/how-much-entropy-is-lost-via-hashing-when-you-add-known-or-low-entropy-data