What does this solve the that the other far more mature tools don’t?

https://www.cryfs.org/

For example, has been around for decades. Is widely supported and battle tested.

If this is a real thing, it needs a lot of work. Lots of failure modes, errors that are not being handled, sometimes exceptions, sometimes swallowing and printing to stdout, very inconsistent style, mixing and matching all kinds of C and C++ conventions, the fallback hard coded path of your specific user name + deep path ...

I would recommend not using this for any data that you actually care about.

I would not trust a thumbdrive with a key that wasn't backed up elsewhere. Those things are unreliable on a good day, and I don't like data loss.