They had at least some level of permission:
> I saw people taking pictures inside all the time, so I just had to double check with an employee.
[...]
> We got situated in the store, double checked with an employee that it was ok to shoot video, and I triggered the slideshow
This "permission" he gets is _extremely_ vague. For all we know he could have asked "hey can I take pictures in the store" and a part-time associate said yes because that's the general policy.
I think it's clear that it was done with a sense of "it's legal so i'm going to do it" even if that wasn't verified nor approved by anyone.
Like, just because a (potentially misinformed) McDonald’s employee told you, that you can eat your own food at the place doesn’t mean it is actually the rule of the place. And on top of that, in this situation it was even illegal.