This has repeatedly my been demonstrated to be false in real world tests. One bundled file performs way better, especially when you take tree shaking, minimization (which has performance implications even after load in terms of memory usage), and compression into account. A small change in one part of the code can result in lots of other code being removed from a library you use. Code splitting usually does a better job of achieving the (suspect) goal of making these incremental changes more performant since the chunks are chosen in order to optimize this vs files which are “chunked” along human organizational lines, which do not necessarily correlate highly with diffs.

If browsers hadn’t removed the shared cache for script resources, there might be an argument here. But they did, putting each domain its own cache to avoid fingerprinting, so even that goes out the window.

On the one hand people worry about the massive node_modules folder in the cases where it doesn't matter (when it's just files on disk in a local node app), and on the other hand, we create things like import maps that will literally take this dependency graph and translate it one-to-one to a higher latency HTTP version, where it absolutely will be a problem.