The problem? XC claimed they implemented multisig. People asked them to show an example of multisig address in their blockchain, the dev posted two links showing only the regular XC addresses. Then some138 created real XC multisig addresses and show them what it look like.

From the posts here I can see that XC never implemented multisig in the coin, otherwise it will be very easy for them to show a multisig address and tx associated with that address in the blockchain.

For mammothcoin, you find tons of multisig addresses and tx associated with the addresses. You know they actually implemented it.