I'll note that when you have a bolt action receiver accurized the gunsmith will true the face of the receiver and recut the barrel threads so they're perfectly straight with the bore. When you're building a custom precision rifle you're already using a match grade barrel, though, and you're doing everything you can to squeeze every last bit of accuracy of out of it. In theory having some misalignment of the barrel with the receiver may affect accuracy on an AR, but I doubt if you'll notice any difference unless you have a very good barrel and have eliminated all the other variables. I would do it on a precision AR with a heavy match grade barrel, but probably wouldn't bother otherwise.
