Was it pretentious of Lincoln to start the Gettysburg Address with "Four score and seven years ago"? Why didn't he just say "Eighty-seven years"? The answer is obvious. The former rings; the latter flops. Adhering to Mr. Orwell's "rules" would rob language of its color and most of its impact.
Good point. In his own day, Churchill had a particularly soaring rhetoric and that helped Britain to survive.
But that was also the time when you had a particularly low and coarse rhetoric of abuse: lackeys, jackals, hyenas, etc. Even Churchill's own rhetoric sometimes led him to make the wrong choices.
Orwell wasn't in any position to law down the law for people. Sometimes his "decent, plain man" routine can wear a little thin. His voice was just one of many in the noise of the time. But it was worth listening to more than so many of the others.