Just about as canon as anything in Japan ever gets, really. Fate's becoming a real clusterfuck in that department, what with Jeanne d'Arc's Fate/Apocrypha design being featured in Fate/zero promotional art and Apocrypha as a project getting some sort of a revival in TYPE-MOON ACE next month---the same magazine that featured Fate/strange fake three years ago.
The real question is whether or not Enkidu's going to make a flashback appearance in the Fate/zero anime with his Fate/strange fake design.
But then again, TYPE-MOON's a damned multiverse anyway. Everything is canon inasmuch as nothing is canon.