YouTube let’s you download your uploaded videos. I’ve never tested it, but supposedly it’s the exact same file you uploaded.[a] It probably wouldn’t work with this “tool” as it uses the video ID (so I assume it’s downloading what clients see, not the source), but it’s an idea for some other variation on this concept.

[a] That way, in the future, if there’s any improvements to the transcode process that makes smaller files (different codec or whatever), they still have the HQ source