There were some videos on the internet that shows you get to pay bitcoin as an option in El Salvador, they're not enforcing it that everyone should buy bitcoin to buy goods.
It's true that merchants and buyers can freely choose what they're up to with what they want to buy. This is really the development that should be welcomed by their people but it's also expected that not everyone is going to welcome this development as there are some protests that happens there because of this.
This choice is also very good. Many people may not understand Bitcoin or the value of Bitcoin. They are unwilling to use Bitcoin for payment and can choose to use the payment method.
Many people who want to protect their privacy will give priority to using Bitcoin for payment.