Hi @MatthewBrown8. Thanks for the response but unfortunately your suggestion is not a solution to the problem. As @PegGronemeyer1 says below, changing the color doesn't change the halo effect and the ability to see your selection one bit. The example @PegGronemeyer1 attached and the one I attached to my original post displays the issue very clearly. Try it yourself: Take the same data set of points and throw it into ArcMap and ArcPro. Symbolize those points to be black dots (or any shape of your choosing) under the size of 10. Set both reference scales to 1:24,000. Select a subset of your data in both applications. Zoom out to 1:60,000 (I know this is beyond the reference scale, but it's a very common thing to do if your data cover a large area, or even a USGS 7.5' quadrangle, which is 1:24,000 scale. Point is, don't get hung up on the fact that it's past the reference scale). Now, can you see which points are selected in ArcMap - Yes. Can you see which points are selected in ArcPro - No.
For some reason, the issues isn't as bad with lines and polygons.