Reloading the game actually put more striders in the air for me- I had a 2x2, 1 block high pit of lava surrounded by barriers and with one strider in it. Upon reloading, it put that strider in the air at y=16 (i'm on a superflat world). This may also apply to things like resource pack loading and unloading, as that reloads the game without exiting the actual world, since I was working on a resource pack when I noticed this change. This also happened with unsaddled striders, and I used no leads.
never mind im dumbass