This is not strong evidence. While, ideally, the behavior you describe should not happen, there are many reasons it could arise. (Bugs, font sizing comes out differently at printer resolution, paper size is different than on-screen page size, different implementation for printing, etc.)

Given that Docs nowadays uses Canvas to render the document being edited, how would it even be possible to delegate rendering to the browser? (Not to mention the challenge of live rendering of pages, footnotes, etc.)