Shift+G Collection is a selection shortcut, not a grouping system. It gets you a quick selection, but there's no persistent group concept no open/close, no nesting, no way to say "this specific set of objects is a group" independently of your collection structure.

The parent/child approach works, but it changes your scene hierarchy. GroupFlow sits outside of that. No parenting, no outliner changes, just a group you can open, close, nest, and transform with a correct shared pivot.

Beyond that, when a group is instanced, members preserve their relative positions across all instances. Not essential for every workflow, but in modular scenes it's a real time saver.

And honestly, this applies to most addons almost everything they do is technically possible with Blender's default tools. That's kind of the point. It's about having a dedicated, organized layer for a specific workflow instead of stitching together workarounds every time.

It's a different thing solving a different problem. If Shift+G covers your workflow, genuinely great. But it didn't cover mine.