When I was a child, my parents had me work on a lot of puzzles. They saw this as a way to build attention span, ability to focus, and persistence to achieve long term goals (not to mention that we had the coolest, most intricate puzzles). I would probably work with my children work on something a bit more constructive and realistic, but the point is that as children we build intellectual habits and attention span from what we do, and being unable to focus on highly addictive stimuli for more than five minutes is a symptom of a strong deficit. One might even consider it an intellectual disability.

I think GP means it as a symptom. If you can't remain on a single game (which is supposed to be a highly entertaining, dopamine-optimized experience) for more than 5 minutes, what is the likelihood you can stick with any harder task in everyday life for longer?

Plenty of valuable things are less exciting than a video game in their first 300 seconds, and last much longer than 5 minutes.