With ANY stove, no matter what fuel, you will need an air supply for combustion. I think that is pretty obvious.
The air *could* get to the fuel/flame by coming down between the pot and the windshield, but that is pretty unreliable and cools the pot. Far better is for the air to come in from underneath, so the hot gases rise up beside & around the pot.
Inadequate air could lead to CO emission as well, although you would have to be pushing for that to happen. But why take the risk?
I have windshields with holes at the bottom, but my experience has been that the holes weaken the aluminium a bit. Since my windshields get rolled up and unrolled an awful lot, I prefer plain foil without weaknesses. But, ymmv.
I usually wrap the windshield a bit more than 3/4 of the way around the pot. I do not try to close the gap fully.
This would be pretty typical. There is a significant gap on the downwind side which allows me to get to the control valve easily. More than this is certainly not needed.
I don't close it up any more than this for two main reasons. The first is that I usually cook inside my tent where there is some shelter to start with. The gap does not cause me any problems with wind. The second is that closing the gap any more is not really worth the effort - I'm lazy!
Even under extreme conditions (and this *was* a bit extreme!), I would still have about that much gap. You can't see it here because the gap is pointed downwind, but it is there.
Would a small notch be adequate? I would prefer something a little larger than that, just to make sure the air flow is adequate.