So, pilots can use their iPads during all flight phases. But I am forbidden to use mine (in flight mode) from the door close to TO +? and from initial descent to door open.
But I can distract myself with newspapers, books, magazines.
IMHO I believe nobody wants to change the rules 'just in case' something might happen and then they would get their nether regions sued by unscrupulous lawyers.
When instructed by the crew I diligently turn off my iPad (actually I put it to sleep by closing the cover) and grin. My better half, on the other hand, shushes me when I tell her to pay attention to the safety announcements and returns to her (bodice-ripping) book.