Most likely not: they will reprice the ticket as one way and refund the difference. If one way is more expensive than what you've paid, they would usually refund the taxes of the return leg at least. The 125 EUR penalty is charged in case you show up for your return flight without having flown the first leg.
With AF ticket structure, they would certainly reprice the outbound leg using the cheapest one way that has a higher booking class in the hierarchy than what you've booked, if your outbound booking class does not have a suitable one way fare attached to it, meaning there is no one way fare in this booking class that can be bought at your ticketing date for your departure date. This seems likely given your example.

Here is what I believe would be the hierarchy used by AF:
J9 C9 D9 I9 Z9 O9 Y9 B9 M9 P9 U9 F9 K9 W9 H9 S9 L9 A9 Q9 T9 E9 N9 R9 V9 X9 G9

The thing is that they might still sell round trip in E class but shortly before departure there is no "suitable" E fare one way, and the cheapest one way fare theoretically possible (taking into account ticketing date and date of departure and flight used) is certainly a T fare (the WK brand or something like that). However, even if E is available, they can also make intermediary booking class unavailable (like P to T), meaning that one way, you must buy an expensive M class. In this case, rather than buying M one way, you could buy E+G round trip, buy G as FLEX, and ask for a refund of the return leg. They would not know what booking class was available at time of booking, so they would just go up the hierarchy until they find a one way fare that complies with all requirements (like a T fare) and then refund the price difference. So you essentially buy one way in T with this scheme, although only M was available outright. Technical and complicated, but rather sweet, isn't it?

However, if you don't need the flexibility, you should buy Light/Classic both ways, save 160-200 EUR and find a return throw away leg with the cheapest booking class, by staying more than a week and less than 6 months in HAJ. The return leg would have a value of 50-100 EUR that you lose, but you save the flex additional fee and you don't pay for the reprice to the "next possible one way booking class".