@24victor
I certainly did read what you posted. Your definition of a single point failure, as applied to pitot tubes in this case, really doesn't make any sense. That is what I was trying to get at in my post. Saying that something which is triple redundant can have a single point failure because all three failed at once makes no sense. If ALL systems of a redundant system fail, that isn't a single point failure, it's really bad luck.
I see what you're getting at by saying that icing causes the single point failure behavior. However, each system is designed to mitigate these risks individually.
It's a design issue, not coping with some worse than expected environment, that makes a single point failure.