I explain this bug with following example:
open "cmd.exe" then open another "cmd.exe"
in this case "auto group" is on but it open second "cmd.exe" in new window.
when i group those two "cmd.exe" and open third "cmd.exe", "auto group" works properly and it open in those group.
edition: windows 10 pro
version: 20h2
os build: 19042.630
groupy version: 1.44