Yes it would. GSM uses 2-3 milliseond pulses of varying intensity. One device in the phone can have as much as 50 times the average drain depending on conditions. The definition of "current" rate is very dim. It's very different from a light bulb.

You need to construct averages (software or hardware) and that requires hardware itself. Even if you try estimates by looking at the terminal running lshal every second, when you close the lid your figure just quadrupled. Simply moving around the phone varies recv signal and that affects tx signal. Older models varied emissions between 4 mW to 4W (I think that's been lowered since though). Signal strength alone can have a thousandfold increase over a few milliseconds.

Don't mean to be difficult.

I simply don't think it's doable with any useful accuracy.