I had a similar experience.
Once I backpacked with a guy with wall climbing credentials far above my skills.
However on a relatively easy ridge/slabs route I had to lead because this guy was not comfortable leading there.
It can be explained by the fact that he spent more time on rock walls and I spent more time on relatively easy mountaineering routes.
Vertical wall, moderately steep snow/ice, scree or steep grassy slope or bushwhack require different skills. These skills can be learned through experience or special mountaineering courses/schools.
Wall climbing "expert" without any mountaineering exposure may not have the broad enough skill set for a relatively easy mountaineering route with diverse conditions.
