I feel (i.e. just my own subjective experience) it's not only the formation of memory that benefits from mental "down time" but also the gradual solution of abstract problems, such as the ones we come across in building complicated information systems.

I'm not sure about this:

>> we should aim for “minimal interference” during these breaks – deliberately avoiding any activity that could tamper with the delicate task of memory formation. So no running errands, checking your emails, or surfing the web on your smartphone.

Whilst I agree that cluttering up the brain with other similar sorts of information (so stuff in emails or web) is counter-productive, I feel (again just my own experience) that undertaking a completely different sort of activity which exercises the brain in different ways (so for me things like a bike ride, chopping firewood, kicking a footy with the kids) can have great results. Getting back to the original task, I do often find progress has come out of "thin air".