I think this is the winner. It's one of those love/hate things with this technology. I love how you see creative solutions to stuff like this. But I hate how something so simple is so hard!
Here is a possible variation where you display a polygon using point symbology at its centroid (see link below). You might still have the leader line running over it, so the transparent polygon symbol Linda suggested might still be needed. You can have multiple "symbol layers" under the structure (the wrench icon) of the symbol properties. They call the symbol layers marker, stroke, and fill, which correspond to points, lines, and polygons respectively. With any luck, the leader line will attach to the outer one, even if it's transparent. The advantage to using point symbols for polygons is that you only need one layer on your map to draw both the markers and the labels.
https://community.esri.com/t5/arcgis-pro-questions/arcgis-pro-collapse-small-polygons-to-points-as-i...
Changing requirements took this project in a different direction and I removed the problem layer from the map. I'm not sure if I'll ever loop back on this, but I'll try to update this if I do.