That is true but it can be done without using a pinion depth gauge. That is why you do have to use the gear marking compound.. that is the final test. Yes it takes a while to get it done and I personally would not have done this to my daily driver so I have time to get it right.
MHO it doesn't make sense to hear someone say I can rebuild an entire car yet will not touch a rear end. If you have a passion/hobby for something then do it no matter what anyone says.. may take you longer than the PRO's but who cares now you can say that you've done it yourself.