Original title of "Soleil rouge" / "Red Sun"?

Concerning the original title, https://help.imdb.com/article/contribution/titles/title-formatting/G56U5ERK7YY47CQB says: "We use the original title of a movie/show in its original language as it appears on screen (on the title card) in the opening credits."

I've just watched the film Soleil rouge / Red Sun (1971) in France (restored version), and the title that appears on the title card is "Red Sun"; "Soleil rouge" just appears in the French subtitles. But the original title in the IMDb is currently "Soleil rouge". Is there any reason or is this a mistake?

Note that this is an international production (France / Italy / Spain), and both the film and the credits are in English.