I'm 6'7 and the first time I used a riser was on an 01 Mtn Cat 800 using basically a 4in alum block. The height of the handlebars is not just height & geometry to your body, but also your fitness level. Take power lifting for instance (Which I used to do). When your tall and thin, trying to deadlift a tall guy has to reach down practically to the top of their ankles to start their pull where short guys don't have to reach down as far to start their rep in a very different position than the tall guy. Yet, the guys in strong man are typically tall monsters, like Hapthor Bjornson, when it comes to deadlift with a few exceptions like Eddie Hall. Eddie, had to put on an unsafe amount of weight to pull that world record off the ground against those big guys. Not that the deadlift is more comfortable for the tall guys, they have the size, strength and geometry to pull that heavy weight and they have been doing it daily for a long time.
I think a lot of these pros can run a short bar without discomfort in part of their height but also fitness level certainly makes a difference as well. Guys that are shorter, get more seat time throughout the year to keep those muscle groups they work constantly. And here we come to ride 3-6 months of the year like the guy that breaks a bow out a couple weeks before deer hunting and pulls his shoulder out trying to pull the same weight he left off with last year. Meanwhile the guy next to him, same height and build has been shooting archery nearly the whole year with no aches. So yea, those pros tall or short have the muscle groups trained up where it does not bother them.
Me, nowdays I'll pull a deadlift from the safety braces of the squat rack like a cheater because I don't lift every day and really unless your competing or wanting to simply perform the form the deadlift is the most risk with the least reward for working out. I believe bar height is the same, unless your riding throughout the year, your back probably won't do well in the long run. So use the "cheater bar" and go with an extended height bar and or add an extension until 1. your able to minimize soreness at the end of the day while still maintaining good control. Another thing I consider is how far up the bars are sticking as they can become a giant lever to bend or break the steering post by a simple quick dump of the sled on it's side or rollover. (I've had to replace the steering post twice running a total of 10 inches of extension before.
And no just because were taller doesn't mean our hands are proportionally longer or bigger to other parts of our body...just our dicks... true story...ask your mom!