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.
Lawmaker could easily argue you owe them BTC tax, if you make BTC profits from alts. The only reason in other countries that BTC based profits are not taxed is because they don't accept Bitcoin as currency. In summary, you can't send them profits that they don't or can't accept. El Salvador have taken a different role it seems, they accept your Bitcoin profits from altcoins I image, and will probably expect it as well.
This is probably one of the only downsides of a nation accepting Bitcoin as currency, having to send them BTC from altcoin profits... it also sounds like a small price to pay in the long-term.
However does this mean you don't owe tax from fiat currency profits, if you return it to the nation's currency? It's confusing

It sounds to me like you have a preoccupation with shitcoins. Your previous voluminous post about falling bitcoin dominance being likely to prevent further BTC v fiat gains; a chart to try to show some similar point; and now trying to argue that a downside of El Salvador's pioneering move to accept bitcoin as legal tender is that you might have to pay tax on profits from shitcoins.