Me and my team made that plugin. It initially came from the same org that makes Bazel (rather than the other way around), but I think there's now a small team in the Android org that support it.
Nevertheless, Gradle is currently much more popular than Bazel for Android development so it makes sense that this is where the focus is.
Do you know if any real, non-trivial Android apps are being built using only Bazel?
The majority of all Android apps produced by Google are, and I have worked on one myself.