There're also other things about Electrum 2.0 seed that I want to nitpick, like, if I'm not mistaken, Electrum wallet doesn't forbid using existing standard (single-signed) seed as a multi-sig cosigning key, and vice versa. Therefore, it's exactly the same problem of "only having the 12-word seed is still not enough", isn't it - if you enter a multi-sig seed as a standard (single-sig) one into Electrum, it will show you a blank wallet with 0 balance (typical symptom of "BIP39 derivation path syndrome"); if you forgot to take good care of such a dual-role seed, your co-signer/co-owner will probably blame you (because the co-owned funds might be stolen or permanently locked out).

Also, how could Electrum 2.0 seed achieve its amazing feature of validating a seed without knowing the word list? The answer is: vanity mining. Electrum does vanity mining on its seed in order to embed their version bits into the seed phrase. That explains why Electrum wallet GUI often seems to lose responding for several seconds during generating new seed - because it's still busy finding the required vanity seed for you.