Yes very true about all the phones trying to update together and causing a big rf energy surge. I alluded to that problem in an earlier post. (what actually happens is explained here:
http://www.privateline.com/PCS/callprocessGSM.html). The simple fact is the cost of protecting aircraft systems against this type of radiation is probably very expensive. Simpler to just get everyone to turn their phones off
A not unreasonable conclusion in my opinion.