I don't understand this. The vertex paint's "erase alpha" brush sometimes works and sometimes doesn't. On the right, the brush works properly on one material, but not on the one on the
Photoshop in Blender: Layers and Erase Alpha in texture paint mode (Test 003) - YouTube
Brush — Blender Manual
texturing - How to start with nothing on texture, then paint texture on? - Blender Stack Exchange