To me it seems that modern apps don't really stay frozen in the background like it was ten years ago, at least not on Mac. Something always keeps bubbling up in the process manager. Especially, JS GUIs seem to constantly occupy the CPU with something, even if a little―despite the supposedly event-driven nature.
How do you arrive at that conclusion considering that nowadays browsers tend to run each page in dedicated threads and in some cases even processes? In that scenario your assertion would only hold if you assume no one has more than a couple of pages open at any given time.
