The original French text of the Edict of Nantes address "religion prétendue réformée" or in other words, Reformed Christianity in the English translation.

However, context is important here. The Reformation started in France before there was a clear vision of whether it would result in a separate church and religion, and what its beliefs would be. Therefore in the early 1500 the term "Lutheran" was used as a catch-all phrase regardless of the exact denomination. Simply put, the lines demarcating denominations weren't yet clear.

Over time, Calvinists / Huguenots became the largest Protestant denomination in France, by far. The term "Huguenots" then started to be used as a catch-all phrase for all Protestants, although in reality they were a very large majority among them. More importantly, this was the term used to refer to the Protestant aristocrats involved in the Amboise plot in 1560 to kidnap the king and wrest control away from the ultra-Catholic House of Guise. Realistically, all of them were Calvinists.

Thus in many French and English language articles addressing the Edict of Nantes, the term "Huguenots" is used although it really encompasses all Protestants.