Meh, sorta. There's a range of which you get no vibration. In other words, if it's "close enough" you're ok. That "close enough" varies so it's best to get it as close as you can. It has to have that range, because as you saw in the video Del posted, the driveline angle is constantly changing while the vehicle is in motion.
I get it. What it tells me is that my crappy worn out stock leaf springs (that are essentially flat almost inverse) that I installed my 8.75 rear on are probably allowing crazy motion. Good thing my ESPO's just arrived.
I will have to check the angles again after I get the ESPO's installed, that was the reason for my questions.