PS: I have booked another Euro flight (to GVA). 4 days out, it has a similarly random seat map during the booking process. Fun fact: after having finalised the booking I checked the seatmap again, and suddenly the seat map is wide open! Still with a few random grey seats, but otherwise wide open. Whereas for the first flight mentioned in my OP, the seat map still looks random.

Serious question: does someone have any further insights about the logic of seat maps on Air France in European Y? I have never seen anything like that in European J class, but often in European Y class and French domestic flights from ORY.

The other thing I try to understand: during the check-in window (30 hours before departure) I often see that the seat next to my window seat is "occupied", i.e. with an X rather than just greyed out. I then always wonder whether that means the seat is really occupied by a person (which would lead me to wanting to change to somewhere I don't have a neighbour)? Or is it just blocked off because me and/or the person in the aisle seat are status card holders (Gold and above I presume), in which case I'd happily keep that seat? If it is a blocked seat, why not just grey it out rather than show it as occupied, especially since other seats on the same plane are greyed out?

To me this looks like one of those SNCF moments at Air France: easy things made complicated for no reason. But maybe there is some logic, would love to hear from others what it is.