bflat has somewhat different set of goals and offers "zerolib" and "uefi" runtime target flavours. Its author is also working on the official NativeAOT, which bflat builds on top of :)
There are other niceties like dehydrated binary sections, metadata compression, linker that is deeply aware of the type system, etc. to keep the binary size scalable as you keep adding dependencies. I'm seeing even smaller sizes with .NET 9 preview.
