Previously unpaved way gets paved with asphalt, StreetComplete user changes surface=gravel to surface=asphalt without being aware of (i.e. without editing) paved=no → confusion
it makes data less confusing, especially if surface= is later edited again
surface=paved paved=yes is duplicative and mildly confusing, if you get surface=paved paved=no you need to start looking at data what is going on
so it is better to clean it while it is merely duplication
also, it makes easier to manually investigate remaining paved=
And that was how this proposal was triggered - after several cases where human brain was not really needed I looked into it and scale is large enough to make mass edit worthwhile.
I plan to look into it, but first would need to process decent sample of cases to check is it safe (often I run out of cases before I checked enough to be sure that bot edit makes sense)
There is also surface=unpaved, so paved=no could be moved to surface=unpaved iff no surface is tagged yet.
There are only 2589 uses of paved=* in total. 2378 of those are no or yes. The remainder are mostly values like asphalt or unpavedwhich could be moved to the surface tag iff there are no conflicts.
I agree that removing duplicate information will reduce confusion. An automated edit should be able to remove almost all occurences of paved=* and the few remaining ones (i.e. conflicts) need to be investigated manually.