CDG is the only airport I know where it’s SOP to intercept the extended centreline even if not cleared unless the controller has specifically not told you to. As 95% of the approaches we fly are still ILS, I’d still disarm Nav and arm LOC instead.
The only time I’ve left Nav in blue is when cleared for an RNAV approach but on a heading. I’d extend the centreline from the FAF and leave it armed.
Champ