The only thing that leaves me confused is that BTC is legal tender in El Salvador, and the blueprint of the law defines selling as "changing into a legal tender".
So maybe BTC is an exception to the rule and "taxically" untouchable?
... or maybe the lawmaker could argue when you
buy bitcoin or swap some shitcoin for bitcoin, you're also "cashing out" the (crypto)currency into a legal tender - so you owe CGT.
You never know what byzantine concepts the lawmakers are going to come up with.
That is already in place in Australia... It is considered a dispose at the current Shitcoin/AUD pair... and Capital Gains TAX to be paid or Capital Loss to be carried forward...