Usually when using the elytra and beginning to loose altitude the players legs would flail around a little as if they were walking or trying to gain balance, the speed of this somehow has been increased dramatically, resulting in the players legs rapidly sprinting instead of doing their usual glide
Tough to explain but I tried

This is the action I am referring to, when the players legs are in motion, when you start to fall they tend to rapidly speed up in an unrealistic manner