Bitcoin XT is an alt the same way Electrum and MultiBit are alts.
I'm going to have to disagree with this, but I understand why you're saying it. In a sense, Bitcoin XT is an alternative wallet for Bitcoin, like Electrum and MultiBit are. This supports what you're saying. However, Electrum and MultiBit (AFAIK) do not change the consensus algorithm. Bitcoin XT is about to change the consensus algorithm.
Suppose Electrum updated their wallet so that it would check a different POW algorithm than sha256 after a certain block height. It's clear to me that after that block height it would no longer be a wallet for Bitcoin. One could argue that it's no longer a wallet for Bitcoin as soon as the alternative code is released. It might agree with Bitcoin for a while, but the fact that the consensus code is different means it isn't the same coin -- it will just appear to be for a while.
Bitcoin XT is in the process of changing the consensus code. I understand that the people who support this change will insist on calling it "Bitcoin." But if both chains survive, it seems like the one following the older consensus algorithm has more of a claim to the older name.
I know that the official position of those in favor of bigger blocks is: the old chain will not survive. I'm not sure if this is wishful thinking or a strategy to keep people who support Bitcoin (as it is defined today) from trying to see it through this crisis.