I don't understand what you mean, if he saves the 3 seeds he won't need to save also the 3 private keys to be able to sign the transactions because he can already spend from the wallet he accessed with the seeds.
In a 2 of 3 multi-signature wallet, you need two of seed phrases for signing transactions and all three master public keys for generating the wallet.
If you save three seed phrases and don't save any of master public keys, you will need all three seed phrases for making any transaction from your wallet and as mentioned by LoyceV, your wallet would be like a 3 of 3 multi-signature wallet.
You should save master public keys too, so that you can be able to spend fund even if you lose of the seed phrases.