That is actually the defining characteristic of legal tender: “money that is legally valid for the payment of debts and that must be accepted for that purpose when offered”

https://www.merriam-webster.com/dictionary/legal%20tender

Thanks, you're right and I was totally wrong. I'd delete my comment if I could

Its status in El Salvador was actually a bit more than _just_ legal tender; merchants were _required_ to accept it.

For instance, the euro is legal tender in the eurozone. I can pay a tax bill or a bank loan with 10cent coins, and technically they have to accept that (though note that some countries do have special rules around whether small change is legal tender). However, a merchant is not required to take my wheelbarrow full of 10cent coins in exchange for goods and services; no debt exists before the purchase.

El Salvador was forcing the merchant to take the wheelbarrow.

"El Salvador abandons tulips as legal tender"