Good observation.

I have my coached athletes do a couple things to address this unique movement (french technique somewhat sideways to the hill).
1) Box step ups. I have them step up and down off all 4 sides of the box. Front to back, for sure, but also side to side. This will hit those aductors.

2) When out for hilly hikes or runs, i have them ‘french technique’ up the steepest hills. Ideally facing across the hill (hips 90 degrees away from fall line) and crossing over with that downhill foot and stepping up. I tell them that if this starts to ‘burn’ at all or skyrocket the heart rate, then to switch back to a normal uphill-facing posture.

Good question.
Steve