97.5% of nodes don’t have tags and only contain latitude and longitude data. [0]
Only 0.01 % to 0.05 % of the nodes are distinct nodes with the same coordinates and majority of them have been created by error. [1]
While there are some cases where a node provides an additional information for a way, it would still be much better, if ways would contain geometry directly (instead of node IDs) and encode that additional information differently.
If way's coordinates contain altitude as 3rd dimension, it can just store three-dimensional geometry. Any layer tag, on a node that is part of a way, could probably be moved to the way itself.
[0] https://media.jochentopf.com/media/2022-08-15-study-evolutio...
[1] https://github.com/osmlab/osm-data-model/blob/master/geometr...