What a load of bollocks. I have had iPads above 12000' cabin altitude and there is no such warning. I've also spent weeks with them living at over 14000' at times up to 16000', downloading photos from cameras and doing other high workload tasks.
Secondly, I have a document here showing Airbus testing the iPad to 50,000' for 20 minutes. This document forms part of the iPad EFB certification of the airline(s) to use them in the Airbus cockpit. I'm sure Boeing have similar.
Again, I call that screen explosion due to altitude malicious scaremongering crap.
And from apple's own website:
Operating altitude: Tested up to 3,000 metres (10,000 feet)
That is
NOT a limitation and exceeding it is not a warranty voiding event. That's just the tested range. Two very very different things.