It should be TBS upstreaming their work in that repository to the kernel, but for some raison they don't.
TBS has a love/hate relationship with upstreaming. All the people trying to use their devices and/or sustain support in distros are in favour of upstreaming and a couple of years ago they caved into the pressure and started releasing on GitHub which provided a consistent/common source for them. At the same time this has made it easier for cheap Chinese knock-offs of their boards to be produced so part of their team would like to revert to the less accessible "download tarballs via website" approach they had in the past. I'm not sure what the solution is, and it's a hard problem for a small manufacturer so I'm not sure they do either, so I wouldn't expect much change. Most of the drivers are rather messy anyway so the upstreaming process would need a ton of patience and persistence.