This doesn't make sense in a rather fundamental way - there is no way to design a real computer where doing some useless work is better than doing no work, just think about energy consumption and battery life since this is laptops. Or that's just resources your current app can't use
Besides, they aren't that well engineered, bugs exist and last and come back, etc, so even when on average the impact isn't big, you can get a few photo analysis indexing going haywire for awhile and get stuck
This take expresses a fundamental misunderstanding of the whole problem domain. There is a workload comprised of hundreds of processes, some of which multithreaded, that need to be processed. That does not change nor go away. You have absolutely no suggestion that any of those hundreds of processes is "useless". What you will certainly have are processes that will be waiting for IO, but waiting for a request to return a response is not useless.
This is far from being a hypothesis. This is an accurate description of your average workstation. I recommend you casually check the list of processes running at any given moment in any random desktop or laptop you find in a 5 meter radius.