Bitcoin Cash is the true bitcoin because it MAINTAINED THE BITCOIN LEDGER, while also STAYING TRUE TO SATOSHIS VISION.
If XCPC wants to be the true and more useful counterparty, just do the same thing. Maintain the Counterparty ledger. And fork to the version of bitcoin which is actually useful, low fee, high capacity, and maintains Satoshis vision of peer to peer electronic CASH.
If bitcoin cash had just created a new altcoin with bigger blocks, but no ledger, it would NOT be the true bitcoin. It would simply be yet another altcoin no different from litecoin or dogecoin or 100 shitcoins, that was sha256 but with 8mb blocks instead of 1mb. And no one would care.
But Bitcoin Cash IS THE TRUE BITCOIN. And it fairly maintained the ledger of the true bitcoin, the one originated by Satoshi in the genesis block. The one with every transaction in bitcoin up to the point of the fork. The one with the original counterparty burn in it.