You don't need to be on the same band as the smoker.
Without knowing what kind of signal strength you have in these areas its hard to say exactly what your issue is. 2.4 kind of sucks and you run into alot of issues in regards to interference with that band compared to 5 ghz. Microwaves are notorious for causing problems in 2.4.
Are you an iphone or android guy? There are wifi scanner apps out there that will show you signal strength for each band and that can help identify if the problem is signal strength related or not.
Wifi Analyzer for Android (free)
Network Analyzer for iOS (3.99)
running that will give you a sense of what kind of signal issues you have.
If that first part is correct, then I think the problem is solved. As far as I could tell yesterday, I was staying connected despite me and my phone moving around and presumably switching between 2.4 and 5, but I didn't test it for more than a couple minutes. I was just expecting I might have the problem over the course of 4-8 hours.
Am I misreading or mishearing what the grill people are telling me, or are they just dumb/liars?
I guess I could still see there being some benefit to segregating the bands if my phone keeps flopping between bands as I get closer to the balcony where the extender is and cutting out my connection momentarily, but I'll burn that bridge and light the way if I keep coming to it.
Other than this grill, I've had no range/signal issues. I've got all new crap from Xfinity and it's a 1-bedroom condo that's like 1/4 the size of a house that might need all extenders, mesh, etc. for normal stuff. But I did happen to download that wifi analyzer app yesterday; my buddy who's coming over Saturday for a test run on the grill while we finish off all the remaining 2-person tasks I need to do to finish being moved in told me to get it so we can test if necessary. But I think this ticket is on the verge of being closed.