Sorry to hear that. That sounds frustrating.
I recently asked our head coach (Scott J.) about the same question: AeT HR applied to XC. When new or inefficient at the sport, it won’t apply. There’s too much additional muscle mass being recruited for a running AeT to apply. Using a drift test on a flat course is how you can figure it out.
If running aggravates the injury, then I would try steep hikes. Most ultra races have a lot of hiking anyway, so it won’t be non-specific.