Agree. It sounds reasonable that the datafield should be elevation/ascent.
GC, GCM and the activity history on my watch all report the same ascent (783m) for the ride. And I have not yet noticed any strange or faulty behaviour of the altimeter. During the ride the elevation seemed OK.
Well, no big problem and I can happily live with it. Just curious to see what it was.
Same here in MTB