I had such an experience with OK in PRG to KBP.
No SP holding pen, one line but an announcement was made for SP + STE card holder first, while Coach was rushing at the gate.
I just cut the line (the way Mr. Clooney did in HH) and pop up to the front.
No pity, no remarks, just don’t care. I am entitled to this benefit as the announcement mentionned.

Concept applicable with AF in provincial airport too maybe?

Appropriate, yes. Because there are often many people in that line that shouldn't be.

But effective, no. It doesn't move 80% of the people clogging up the SP line that shouldn't be there. Say your "Non mais il y a tout ça en SkyPriority?!" and the elder French couple who are on a plane for the first time in 8 years using their Cofinoga loyalty points + the un-washed hippie with a 30kg "hand luggage" back peach each on his back, torso and one around his neck + the Greek lady who only speaks Greek + the student on his way to a party with large noise-cancelling headphones on his ears... none of them will move. They won't hear what you say or not understand French or simply don't feel that it's them you're addressing because they simply have never heard of SkyPriority. There are of course different populations for different flights, you may have more luck on a Monday morning at a gate for a flight to Copenhagen (more Paris-based business travelers, familiar with the concept) than on a Saturday morning in July for a flight to Barcelona.

Still, the layout of 2F is such that most people simply congregate around the gate, aren't aware of which line is which and so simply stand there. My sense is that there aren't that many people who choose to stand in the wrong line (=know that they should be in the non-SP line but still use the SP line). For most, it is more a matter of cluelessness than deliberate cheating. If I could combat cluelessness in air travel I would, but realistically it is unfair to expect everybody to be as savvy and familiar with procedures as us FT frequent flyers are. Put most of us in a bus terminal in Bangui or Cochabamba and we'd be lost as well.

I'd also appreciate if they enforced it better, and sending people back to the end of the correct line is part of that ("What? But that means I have to stand in line all over again?" - "I am sorry Sir/Madam, but we made several announcements that boarding is currently only for Zone xx, and there are big signs that indicate which line is for which zone").

On "how to avoid standing in line at the gate and then in the jetway": forget about zones. Even as a zone 1 you have to be waiting at the gate a long time before they start boarding, which means idle time just waiting. Time that could be spent doing something more pleasant.

Instead, say to yourself that there always has to be one person who boards last and that before the screens say "Dernier appel" there still is time to take another coffee at the lounge. And then say to yourself that you could be that person. Unless you play it really risky you'll find yourself behind maybe 6 or 10 people in the jetway. More tricky if you have lots of hand luggage to stow, but then again if everybody is on board already nobody will mind if your put your stuff wherever there is space, including in the J class overhead lockers.

Picture taken in PRG on 08/03 attached.


PRG - zone 0

So on 08/03 you will have :
- Zone 0 : ladies
- Zone 1 : J , C2000, Ultimate
- Zone 2: STE+, Flex
- Zone 3: STE, Y
- Zone 4-5 : Y

« Excuse me Madam, I am only STE+, May I board with you today? »
😂

CDG 2F non-status pax line looks more like an « ŕ l’abordage » mess.
For my EU airports experiences, I only saw these gate lices situations when it has to do with French pax / carriers.