I am not sure that it is a CMAS thing. CMAS is not the official standard. It is a control thing. Diving is controlled by the FFESSM not the agencies. I have never dived in France yet but I have read a lot of stories about unhappy foreign customers or unhappy French divers who certified abroad.
Here is an related story.
On the PADI student record forms and student log book, the instructor has to initial or sign a seemingly endless list of skills and tests a student has completed. On the PADI Americas form for this, in some cases a single signature can be used in lieu of a slew of initials. Back before eLearning, there were initials required showing completion of each of the 5 knowledge reviews and each of 5 confined water dives. That is in case different instructors supervised different items. If the same instructor did them all, the instructions
clearly said that the instructor only needed to sign at the bottom of that section. The same was true for the log book. No problem--everyone in the shop did that. When students were planning to compete their OW certification on a trip, a photocopy of that page was used, along with the logbook, as a referral form so that the student could go right to the OW checkout dives wherever their vacation took them.
One of our students took that referral form and logbook to the resort where he was staying on a
French island in the Caribbean. The shop refused to accept it because all of the individual items were not initialed. The student emailed our shop, our shop contacted PADI, and PADI contacted the instructor to tell him it was all OK. The instructor said, no, it was not OK. They were PADI America. He was PADI Europe. They could not tell him what to do.
So the student had to do all the class over again, at twice the price of the OW certification dives, and he missed out on a couple days of vacation. From then on, all of the instructors in the shop were recreated to initial everything and sign at the bottom, too.