If they only had the seed and nothing else, it might buy some time. But if they also have access to a watch-only wallet, then they can see your derivation path, which is usually not sensitive information.

You are better off using a passphrase instead.

It can but its not secure and it could lead to loss of funds because your self not remembering your setup. And if you write it down somewhere the "hacker" can find it and exploit it.

I think there are better ways to secure a wallet. (passphrase or multisig)

you're talking about only minutes of time bought in this situation though... it's a matter of iterating over the Accounts, deriving a few addresses and looking for UTXOs not challenge.