Does this web page really correctly depict the angle that is called "incidence" in the French language in the aviation context?
Yeah it's right if we consider that the relative wind is parallel to the ground.

In French, the "angle d'incidence" is the angle between the chord line and the relative wind, contrary to the US and UK which it's the angle between the chord line and the longitudinal axis.(fr="angle de calage")


  In french: In fluid mechanics, "l'angle d'incidence" is the angle formed by the chord of a profile and the relative wind speed vector. In English l'angle d'incidence" is called angle of attack (AOA).
  Attention, angle of incidence in English corresponds in French to the "angle de calage", the angle formed by the reference chord of a wing and the longitudinal axis of the aircraft.
  L'incidence (fr) notes : α
  




"Croisière" is cruise flight .the picture of the website is not clear because it confusing chord line and longitudinal axis(perhaps to simplify)... other important notion: RELATIVE WIND is the relative movement of air relative to the plane; it is ALWAYS PARALLEL AND SENSE OPPOSITE to the TRAJECTORY OF THE AIRPLANE(path)

Source: (the second link is french because the same page is different in French and in English)
https://fr.m.wikipedia.org/wiki/Incidence_(a%C3%A9rodynamique)
https://www.lavionnaire.fr/AerodynCPFoyer.php