Centaurus - to try to answer part 2 of your query - it sounds as if the second a/c was 'tight' as far as leaks go - the leakage rates vary significantly between hulls. If the rate is VERY low (which is unusual) then the hull could retain whatever pressure it had for a while hence getting to 20 before the cabin reached 10?
As far as part 1 goes, I have always assumed that 'airmanship' would dictate the other pilot double checks critical systems? I always get my F/O to confirm the press. panel settings when I make them and vice versa.