It would essentially be a “Revert” button modified to save in the background (i.e., without opening it) an unaltered, focus-maximized original of any selected image that had been taken and saved on that particular device.

The modified version of the selected photo that is open on the device’s screen (and continues to be tweaked) would not be affected by the existence of the unaltered original that is being saved 0ff-screen.

What's the advantage?

The TTG button would be a quick way to dig up the most-unaltered originals available when submitting “Before and After” photos to third-party photo publishers when a VUO is not available.