I think I remember I used to run PBRUSH.EXE. I thought that was "Paintbrush". I run PBRUSH now I get "Paint". Maybe I am misremembering "Paint 3D sounds like too much work" as "MS Paint sounds like too much work".
...explains how by various tricks, trying to run PBRUSH gets you Paint, but also maintains that they are just the same thing. Hmm.
Maybe at some point in a series of Windows upgrades in place, there was an older PBRUSH and a new PAINT on the same system, from different Windows versions, and I preferred PBRUSH.