Co-maintainer here. That's basically what it is. The value proposition is included hardware enablement on the image (nvidia drivers, controller support, etc). and flathub ootb.

In the end, it is just an extra layer of testing. Silverblue only provides the base imgaes and confirms its stability. uBlue/bluefin adds the layers on top to the image and tests their stability with the base image before pushing the combined image to users. It is good for people who don't want to do the layering and want something with those defaults out of the box.

Edit: for clarity, my comment is mostly directed at ublue or universal blue, which is what bluefin is based on.

I think the really value comes from the ability to easily roll new custom images and for the community to collaborate on those images to produce images that require minimal layering after the application locally.