Author here! What a surprise. This was an abandoned project from 2019, that we never linked or advertised anywhere as far as I know. Anyways, happy to answer questions.
why (if) was this not picked for further research? i know that oatml did quite amount of work on this front as well and it seems the direction is still being worked on. want to get ur 2 cent on this approach.
BNNs certainly have their uses, but I think people in general found that it's a better use of compute to fit a larger model on more data than to try to squeeze more juice from a given small dataset + model. Usually there is more data available, it's just somewhat tangentially related. LLMs are the ultimate example of how training on tons of tangentially-related data can ultimately be worthwhile for almost any task.
I still am excited by Dex (https://github.com/google-research/dex-lang/) and still write code in it! I have a bunch of demos and fixes written, and am just waiting for Dougal to finish his latest re-write before I can merge them.