Being tossed of from high altitude is and should be a threat, which is why you want high athletics score to resist.
The problem is that it's not resistable at all, at least according to the lack of rolls in the combat log. You seem to automatically succeed.
Shove MUST be a CONSTESTED Athletics checkI'm pretty sure I've seen it resisted, but not very often. Maybe there's something wonky about not taking the skill into account or something. And it definitively should be an action, not a bonus action.