I think this is a bug, but I'll start out as a question.
I want to make a web map using tiles stored in mapbox.
Notice how you can zoom into zoom level 21 in the mapbox viewer.
When I add the mapbox tiles to a web map (Add Layer from web> Tile Layer) I'm limited to zoom level 19.
I'd really like to be able to use an arcgis online webmap to mapbox drone imagery at zoom levels greater than 19 in a webmap.
Is this a bug?