If you really want to consider this case, then, you'll need TWO pitot tubes iced up the same way and exactly at the same time for your system not rejecting the wrong data
it is part of the smal risidual-risk in any security concept with multible equivalent sensors.....
IF they are disturbed in an unexpected way, they can be disturbed all together in the same moment (if a tsunami kills the emergency generator, he can kill also the second-third-and so forth....)