The weirdest thing about the always-on icon grouping is the (lack of?) design rationale behind it. What's the point of saving space in the taskbar? There's no content of any kind there and modern displays typically have ample horizontal space.
I think it depends on the software. I have ended up with dozens of PHPStorm windows, because of a situation where windows would be restored on branch change but not auto-closed. Combining them into one icon made it manageable.
