I've edited my shapefile quite a bit using the Cut and Merge tool (through the Editor toolbox, not the geoprocessing tool). It looks like this:
For some reason, when I export the shapefile to a KML file, it seems to "remember" the old polygons, as though the merge didn't take. The outlines should look identical to the above picture, but they don't:
Is this something to be concerned about? None of my other shapefiles are behaving this way. Before I created the KML file I made sure to save my edits and clear my selected features. I also ran the Repair Geometry tool, and validated my topology (which uses the Must Not Have Gaps and Must Not Overlap rules).
I use ArcGIS for Desktop 10.6.1 on Windows 7.