Ok, seriously. WTF.
Take your own argument into advisement, man!
What I mean is that if bitcoin hard forks, you make two *different* crypto coins. If you think that you "double the coins" then you should take into account all the coins on other chains too, all altcoins.
And that's indeed fundamental. The idea of "sound money" only makes sense if that money has the monopoly on money. The idea of sound crypto money only makes sense if there is one crypto. But if the market is shared with others, then "sound money on one" doesn't make sense. Yes, if there is BTC, and BTC-U, there are 21 million BTC, and 21 million BTC-U. But there are also 7 million DASH, 90 million ETH, 14 million XMR, and so on. If you are worried about the doubling of bitcoin, you should also consider all other crypto.
Bitcoin is not fundamentally different. It is a crypto like any other. It just was there first, and that gives the bitcoin brand name a huge advantage.