Thanks, your link is slightly broken :
https://www.cncej.org/uploads/document/file/11/VADEMECUM_202... I could only find 3 or 4 instances of the word "constatant" in that document. So I'm not clear that there are 3 separate categories of expert. But maybe you just happen to know that there are.
No idea what that would then translate to in the English legal system, although there are clues in the term itself: obviously
constatation does indeed suggest a role limited to observing and recording defects, damage, phenomena, etc.
Maybe you've got the idea of 3 roles from Emmanuella's link. But there it talks of 3 types of activity, and the way I read it, it is just one person: "il s’agit bien évidemment d’
un professionnel ..."