Why do tagged folders do not appear in open/save dialogs?
If you go into finder>preferences>tags you will see that two tags have very similar colours, in my case, "work" and "orange". Try changing the colour of your "Projet" tag and see if they both the files change. If they don't then you might not have tagged your files correctly. 

It seems like a silly answer but this has happened to me before that's why I am proposing this.