Yeah, it's true that in case of 2-3 multisig, if you lose one part of seeds or if someone steals one part of seeds, you'll still be able to fully recover your wallet
As already said in this thread, you can't recover your 2 of 3 multi-signature wallet, if you have lost one of seed phrases and you don't have the master public key derived from that.
Take note that for recovering a 2 of 3 multi-signature, all three master public keys are required. If you have two of seed phrases, two of master public keys are derived from them and you need to have the master public key derived from the lost seed phrase as well.