I don't see anyway they're spending effort policing a walkway. The only way it would work would be if they closed all entrances to the resorts except for one or 2 doors. Then, they could check Magic Bands as you walk in and turn you away if they needed. Of course, they'd also have to do this after exiting the monorail. It wouldn't do any good to check it in advance because if you left MK going to your room at GF, you could get off at Polynesian or Contemporary unless they blocked you at the monorail boarding area.
It's all possible but is the hassle and the complications worth it when they have so much else going on?
I will say it's not an original idea though for Disney. At
Disneyland you have to go through security to enter the Grand Californian. Even if you're staying at the Disneyland Hotel, you can't cut through there without a reason. I know part of the thought process was because day guests at the park were flooding the lobby at Grand Californian taking breaks during the day.