Canter cues... I think I've kind of forgotten since learning to ride at a riding school 10+ years ago.
Personally I hate the outside leg back, it's always made me feel unbalanced so I just stopped using it. Which now that I think about it is pretty stupid of me. All my horses have cantered from inside leg only. And I do something else, not sure what it is, bit of seat, bit of twist, leg but in like an up way rather than a forwards way. And teach them that to canter. They never confuse it. I'd probably have problems if I pursued high level dressage, the instructor would tell me to do something with the "traditional" command and it just wouldn't be practical! But you can train to any cue really. I don't even think about it. I just ride how I ride and if a horse doesn't do it that way I teach them.
Now, 6 years on, I am thinking I should have told this to the buyers of two riding horses I sold
I think a lot of horses have these strange "buttons", just sometimes you don't discover them! Shouldn't be too tricky to retrain.