Frankly, it doesn't matter.
Height and length are valuable pieces of information to have when you're considering drafting a player, or signing a guy who's barely played. That's because those stats give you some insight as to what roles they might be able to play on the court.
Once you've actually got years worth of genuine results of them actually playing on the court, the measurements become secondary: above all, the results are what matters. And regardless of how his height or length stacks up against centres, Julius Randle has produced the goods against both power forwards and centres. So who cares what his measurements are, the results are what matters, and he brings good results. Frankly I don't care if he's 6'7 with a 6'8 wingspan if the end product is what we see today.