You are probably right, just remembered them being forced into something back when. Probably liked to my reading that the FNLAR was originally designed for a lighter round than the .308, maybe this .280.
You are exactly right. It has been a long time ago but I remember reading about how the FN- FAL design dates to before WWII and they were going to use the British .280 (7mm).
When NATO adopted the 7.62, FN was able to use the same platform for it but anything bigger and it wouldn’t have worked.