Hi goingup,
This thread (https://uphillathlete.com/forums/topic/can-the-big-vert-training-plan-be-used-for-hiking-rather-than-running/) might be of use – note the comment from Scott S, “Focus on the duration prescribed rather than distance or gain”. Hiking rather than running would see a large decrease in speed, which seems similar to what you mention about running on flats rather than on trails with elevation gain.