Having custom f-droid repositories isn't that unusual or necessarily malicious. For example the microG project has its own f-droid repo. iirc there's some overhead with getting something into f-droid since they have their own build process, versus just uploading an APK, which might be why they chose that.
Just look at how out of date NewPipe is in F-Droid, it's maintainer just isn't motivated to get new versions of the app building on F-Droid's servers, leaving end users with a half year out of date client that is unreliable to use.
Scroll down the page please and note the prior F-Droid release was Version 0.25.2 (994) - Added on Aug 10, 2023
All of the v26 releases are missing. F-Droid's maintainers just did not build or publish these, leaving F-Droid users with a broken app since early December 2023 until 2 weeks ago, basically 5 months of shipping an app that did not consistently work.
that's not cool. i would much prefer, since they are not two kids in a college dorm, they worked with fdroid to get properly vetted and included.