Agreed. I think it's a wider phenomenon: Google is culturally uninterested in / incapable of marketing an open source project that's less ambitious / strategic

Agreed. I think it's a wider phenomenon: Google is culturally uninterested in / incapable of marketing an open source project that's less ambitious / strategic than e.g. TensorFlow, Kubernetes, Go, Dart/Flutter, or (looking back a few years...) Angular. The next tier I guess is Abseil or Bazel, which have a nice website, nice docs, and some papers/talks but I think still aren't super widely used outside Google. I can't think of anything smaller than those that's gotten any marketing at all. Can you? tcmalloc at least gets internal changes regularly synced to github (since just a couple years ago iirc), vs. the ancient gperftools snapshot that's more widely known. And there are many other projects of potential interest to the outside world (Fibers...) that have been mentioned publicly but not open sourced at all.