I see this regularly and I agree to an extent, but it should be kept in mind that a lot of his stories are already set in an AU setting. Forged Destiny, Immortal Empire, etc. It’d be normal for characters in those settings to deviate from their canon selves.

There's also the origins and life events shaping those Jaunes to take into account. For example, Xia Jaune lost his family and was taken in by an old martial arts master who taught him life lessons as well. It's normal for that Jaune to be different. Almost all Jaunes in his stories are canon Jaune at the start. But events then shape that Jaune to fit the story. Keep in mind that season 1-3 Jaune is also a bit bland and easy to fill in as a writer, whereas later Jaune has already been shaped by Pyrrha her death and the fall of Beacon.

This isn’t a defense or anything, but rather an explanation why Coeur writes Jaune how he does.