Low battery and other issues
I do notice that the battery level in this video is at it's lowest. But that means that the phone will actually use less power when transmitting data or voice calls. In this video, it shows 3.5G. But on Nokia phones that actually means that the phone is transmitting data over a 3G network, in that case the signal might be subject to a phonomon called "cell breathing". That is, more users pr the cell site, the coverage goes down.
According to information, AT&T in the U.S users 850/1900Mhz for 3G coverage and GSM. It also matters what frequencies are used, as 850Mhz goes a longer in terms of coverage when then 1900Mhz is used. This also effects the mobile phone power, as 850Mhz uses 2W but 1900Mhz only 1W.
I own a Nokia N78 and other Nokia phones and I have never seen this problem that they appears to have just made there. How they made it is unclear. But it is clear that the phone was running on low battery and with data connection running, given the 3.5 marking close to the signal bar.
If Apple wants to be believable, they will repeat that test will a full battery.