Operating system: Win 10
Graphics card: NVIDIA GeForce GTX 970
Broken: 2.79b release, also 2.80 2019-05-26 d525c76003b3 branch: blender2.7
Short description of error
Using "To Sphere" on a mesh that has unselected, unconnected polygons, while proportional editing is enabled in any way causes selected polygons to abnormally increase in size as it becomes spherical, rather than staying at a similar size. The size of the outputted sphere is larger when there are more polygons disconnected from the target.
Exact steps for others to reproduce the error
Use attached file.
Press ALT-SHIFT-S (To Sphere default keybinding) and spherize the spikey shape to 100%.