Splitting hairs?
Because there is a right-wing party (LR), and the RN is positioned at the right of this party. You can call it right of right, if you prefer! 😁
LFI is commonly called far-left and is not ashamed of being called far-left. The other members of the coalition are left of center (PS), and Green, so the coalition is called left-wing and not far-left.
Additionally, standards are different in Europe than in the U.S. Even conservative parties are implementing policies considered as left-wing in the U.S. (I.e. social security), and, for example, the Democrat party would certainly not called left-wing (It's more equivalent to Macron's center-right stance).
Why are far-right people ashamed of being called far-right? 😆