Recoil damage for wild charge?

As far as I know, the only move with an effect in Pokemon Go is Transform.

Thunder Shock charges energy pretty fast and the energy bar is always bouncing around so that might be all you are seeing. Maybe look for a "large" Chansey in a gym to test it against (a lot of HP to try several Wild Charges and less return damage to account for).

in raids every mon I have can see it's bar drop for no reason. (might be at 75% and suddenly it's at 60%) I don't notice it as much in gym battles. But maybe that's because gym battles are such simple things that I don't look closely.