We’re keen on this technique. With you (op) stationary on top of the fence giving the cues and your horse trained to step over and line up in either direction (lots of great videos out there) you can then do some really effective desensitizing from above including poll and ear rubs and pressure on those touchy areas like the top of the rump, the flanks etc…
It’s a whole new perspective from the animal’s point of view and in my experience they end up not only accepting it but finding it quite ho-hum and a nice place to be. And it will come in handy for all sorts of future situations, ie; out on the trail, etc…
Having someone experienced on hand is something we try to have in place for those early rides. Sometimes they’re sitting on a steady eddy themselves which can also be helpful.
Good luck!