not sure why you claim it has an excellent UI, it's a very simple UI with the usual toolbar (who has those anymore? I guess that's a Windows thing.) To me, it looks like one of the basic autogenerated MFC apps with a toolbar and list view that I made dozens of in the 90s. I guess I'm spoiled on a Mac and don't need additional tools (or UIs) on Linux.
This IMO has a much better UI than TimeMachine's. It lets you see all your backup tasks in one spot, rather than having to "Select Disk", and it has 100% less space gimmick.
"very simple" is one of the best compliments an UI can get!
It's deceptively simple--looks like there's a lot of information and functionality packed in, and attention to details is apparent.
Contrast this with the too common designed-by-programmer UIs of Windows utilities, and I'd say this looks great.
UI isn't just what's on the page. It's also what isn't. If you look at the authors WIP you'll actually see how much it's been refined over time :) Very simple but powerful is the intention