This argument is pointless. The argument makes no sense without putting in the context of content creation vs content consumption.

Content creation is very resource incentive. If you don't quit any apps ever, you run out of resources. Simple as that.

Content consumption, on the other hand is easy and very optimized. Always have your browser running with 10 pages loaded at the same time you have your music player running and have a movie paused. No problem. Never quit anything.

Then the argument starts to make some sense.