There's no evidence that the NASA reports are accurate and there's no evidence that they are inaccurate. Some pilots may blame PEDs to cover up their own mistakes, and some pilots may not bother to report incidents because they don't want to deal with the paperwork.
Same goes for the number of PED-caused crashes. Crashes are so rare that statistical analysis becomes a matter of small numbers with a high level of uncertainty. There are plenty of security measures to reduce risks that didn't cause a crash yet. Given the consequences of a planeload of passengers going up in smoke the burden of proof should be with those who want to relax security measures instead of the other way 'round.
IF there was any REAL risk associated with the use of these devices they wouldn't allow them on the plane.
By the same line of reasoning you could claim that if there was any REAL risk associated with drinking and driving it wouldn't be allowed after the first beer instead of after the third.
There are plenty of things in planes with a real risk associated. Flammable liquids, carry on luggage, PEDs. It's the
amount of risk that matters. A small percentage of radiating phones is less of a risk than having 100% of phones switched on.