Say you've done everything right and used 3 coldcards spread across 3 geographic locations using 2of3 multisig.
You're feeling pretty proud of yourself, your coins are super safe.
Then it turns out the RNG in the coldcard mk2 was badly/maliciously implemented and is completely insecure. You need to move your coins right now.
You can probably see the issue
You'd probably want to use diversity for this - do 2of3 multisig with a Coldcard, a Ledger, and a Trezor.