It took me a bit to figure out why the general settings > display options > overdue section didn't do anything. Apparently it only works if sorting is set Due Date, Priority (but not Priority, Due Date). As you can uncheck this setting if you don't want the overdue tasks grouped at the top for easy access, I think this section option should work regardless of what sorting option you choose.
It would be also be nice to have a "set all overdue tasks to today" button in the Overdue dividing header at the top of the overdue section.
No it wouldn't defeat the purpose.
I start each day cleaning up my overdue tasks, but this requires scrolling past all of the not overdue high & medium priority tasks just to change the due date for a single low priority task. An overdue section at the top would allow one to easily clean up overdue tasks with the quick menu to new, non-overdue dates. Which would then not have any tasks in it so everything would be displayed by priority then date at that point.
But if you DID think displaying such a section defeated the purpose... uncheck the setting. Everybody wins. Right now, checking the setting doesn't do anything, but it could and still not bother anyone that didn't like the option because they could simply turn it off.
I'm aware that you can bulk change the date of several tasks, but cleaning up say 5 overdue task to "today" would take 8 taps verses 1 tap with a "set all overdue tasks to today" button. This is of course on the assumption that most people want most tasks to finish near their original due date so today is the most obvious choice for a quick button. However this is a side bonus request compared to the main one that the display overdue section setting work in both sorting options.