Elevation gain or loss is ALWAYS incorrect on all Apple Watches
Apple employees at the Centruy City Westfield Mall location will tell you, off the record, that there are constant complaints about how the apple watches don't compute correct elevation gains and losses as you are moving EVER!
Apple is misleading every single consumer to believe they are getting reliable elevation gains and losses while hiking, running, cycling and anything else that included elevation gains as part of your workout.
Edited to add: And they have no fix for it. All their fixes are not that. They know they can't make it work right, but when you call for tech support they put you through a round of support, implying that it can be fixed. Well, it can't and they know it.