No, that's not the case - there's a standard to how protoc exposes plugin options as CLI options that doesn't require the compiler to know about each plugin. It's obtuse, annoying, and badly documented, but it's there :)

The whole situation is extra confusing because some of the core codegen plugins are built into protoc. That's a distribution and version-matching strategy from the Google team rather than a requirement of the plugin system. I'd very much like Google to ship the built-in plugins as standalone binaries, even if they're also bundled with protoc.