The problem with smoking sections was the smoke would waft over to the non-smoking area. You'll have the same problem with wifi.
Maybe it's possible to jam the signal around a perimeter. Maybe not...yet.
Isn't that illegal?
If you're using an active "jammer", then yes it's highly illegal.
However, if you build a RF blocking wall, then it is legal.
Maybe they mean that the area would be designated for people who intend to sit and use the wifi for a long period, whereas the other area would be for shorter sits.
Call it "laptop-section" and "no-laptop-section" and enforce that? (since it seems to be the goal in the end anyways) I've been to places like that and it works.
When I was in Berlin last winter, I noticed a few coffee shops that had strict no-laptop policies at the front but often allowed laptops in back rooms or further away from the entrance. Seemed like a win-win.