You truncated the AF text. It says:
"Such a passenger is not required to pay an additional fee due to a new calculation and any administrative costs if you inform Air France that you cannot, for any reason, use the ticket for that flight and still want to use the ticket for additional routes or, in the case of multi-destination trip, the return routes.
Such communication must take place within 24 hours after the departure time of the first unused route of the outward flight or, if the departure time of the return flight is within 24 hours of unused flight, at least 2 hours before departure of the return flight by calling our Call Center at +39 0238591272. In the absence of such notice, such passenger will be treated in accordance with the provisions of the preceding paragraph."
The second paragraph makes it clear HOW you can inform AF. No other method/timing is considered. Airlines are using the exact language of the AGCM (Autorità Garante della Concorrenza ed il Mercato) back in 2017, which makes it very difficult to use.
If that clause had been widely used since 2017, that would be well known. Airlines have probably succeeded in making it practically inoperational.
But with a verly long transfer (as mentioned above), it would be worth the try.