The scope for the Stable API says of renameCollection:

renameCollection (not supported in mongos, let's wait to see mongos's semantics before adding to Version 1)

But it seems that the renameCollection issues were resolved in 5.0, in scope of PM-1965 .

If that's the case, and there are no other reasons not to include renameCollection in the Stable API, let's consider adding it. The justification is that all the other collection management commands are already included.