This isn’t a solution to your issue, but you might be interested in the discussion of elevation data in this thread: https://forum.inaturalist.org/t/altitude-and-feature-requests/51750/18?u=rupertclayton
As a possible solution to your challenge with the KML file, perhaps you could break up the 4,500 m polygons into smaller departmental places (Junín above 4,500 m, Pasco above 4,500 m). Then you could have a “child” collection project for each iNat place and an umbrella project for “High Andean Flora of Peru”.
If you did create places and projects of this sort, I’d be very interested to identify some of those observations.
If this works well, you might be able to create places for lower elevation slices (e.g. 3,500–4,500 m).