I noticed that the latest stable version of grpc is 1.8.3
But maven central only seems to have https://mvnrepository.com/artifact/io.grpc/grpc-core 1.8.0
Why is that? Why are there no minor releases on the maven central?
Only grpc/grpc (the C-based repo) had a 1.8.3 release.
If you look at grpc/grpc-java's releases you'll see 1.8.0 is the latest 1.8.x release and there is a 1.9.0 release as well, which aligns with what you see on Maven Central. C is close to releasing 1.9.0, as there is a 1.9.0-pre3 release candidate.
There is some coordination between Java, Go, and C's releases for major and minor releases, but none for patch (bug-fix) releases.