It’s kind of buried in the T&C when they redid the program somewhere around 2017 or so but with Flying Blue now there are effectively two different pools of miles- the ones you earn from flying (or using a specific co-branded FB credit card) and the ones you earn from everything else including point transfers from a non-cobranded FB credit card. And these two pools can have different expiration dates on the two year clock based on last activity of that type.

https://awardwallet.com/blog/air-fra...-miles-expire/