Fine tip, @Richard_Sather, and well-explained and illustrated.
The reason we see this so often is probably because this Group by organization is a somewhat newer feature, particularly in Board view, as I recall, so older projects remain in the less efficient and more complex implementation. (And some folks keep building that way, unaware of your post’s approach.)
When following your clean up steps, folks should take care to clear any filters so they apply the clean up to all tasks, not just some of them. I’ve forgotten more than once to clear the “Incomplete” filter, which I typically use, and then have to repeat clean up steps for those tasks that were previously hidden.
Thanks,
Larry