Whether you use an altcoin (or bitcoin) for a long or short-term investment, or because it satisfies you as a medium of exchange, it'd be misleading to call it a "currency". I don't know who began this terrible start of the use "currency" after "crypto", but, in my opinion, it shouldn't be formulated like that since none of them are currencies.

A currency is a system of money in general use in a particular country. For example fiat. Fiat money gives central banks greater control over the economy because they can control how much money is printed. This is how the state works.

Naming them "coins" isn't false, they can be considered as "coins" (Hence "altcoins"). In ancient times, people used to exchange goods with gold coins and there were times when they passed over their national currency with those coins. And that's because they were broadly accepted by anyone, since they were made out of gold.