No, it doesn't.
That's like saying "Will LiteCoin reduce the amount of Bitcoin?"
If there is a fork, it doesn't care about the other fork, it's really just as easy as that.
Well, this doesn't make sense to me in the way I think about things.
If HYPOTHETICALLY at "Zero Hour" the hardfork occurs, and XT wins, but I subsequently choose to run my 1 million Bitcoins onto the old Core Chain - and if everyone seems pretty clear that those Bitcoins can NEVER EVER EVER go back onto the XT Chain - then it seems to me that the XT Chain just lost 1 million bitcoins.
So is my understanding of this flawed? Or are you saying that my Core-Forked Bitcoin are still counted in the 21 Million XT Bitcoins - but just "lost".