You might be right, and my initial assessment is incorrect. The real reason why HTTP2 doesn't solve the loading problem with many files is the depth of imports across all dependencies - the browser loads the entry file, sees its imports, fetches those URLs, then discovers new imports, starts fetching those, discovers more, etc recursively. So the slowness is caused by the latency of each round trip (easily 50ms-500ms), and not by how many files the browser has in-flight simultaneously, as I assumed.