He played for France u-20s until 2012, played full international in 2015. 3 year gap between the step from that level until full status is quite reasonable. Deschamps wanted him, but he maybe got impatient and chose to play for the country of his parents. Nobody noticed though hey?
Senegal must have a number of high quality defenders, I just can't name them for some strange reason.
So he plays some under 20 games, but no under 21 games!! I wonder why that is???