The logic behind this is that, seed words restore only what is publicly on the DAG database about the addresses you had access to.

Multi-sig wallets and smart-contracts are between 2 or more parties, who have paired their devices, info about paired devices is not public, so it is privately stored in your wallet. Bot is just like any other device you would pair with, it just has automated responses.

Private assets like blackbytes and private attestations are also private and not stored on DAG (only hash of the transaction or attestation is on DAG).

So, seed words restore only public stuff, full backup restores everything from the state you had when you did the backup.