The thing is, when you create a new yarn project using yarn init, it will create a .gitattributes like the following:

/.yarn/**            linguist-vendored
/.yarn/releases/*    binary
/.yarn/plugins/**/*  binary
/.pnp.*              binary linguist-generated

yarn.lock is not added to linguist-generated because git by itself doesn't count .lock files

so this extension should probably look for any .lock files by itself