Yeah technically that is the case, because as of now, you have to sell your cryptocurrency into fiat to buy things for most purchases. Therefore, it is a capital gain.
I think in the USA they're looking at a "fair tax law" for immunity with smaller purchases.
Once people are just trading crypto back and forth without changing to fiat, this muddies the waters a little, legally. If you have 1 BTC and you trade it as 1 BTC, and fiat isn't really a thing any more, it hasn't changed quantity, so is it a capital gain?