This article quotes what Gale McMillan said in the late 90's:
http://www.6mmbr.com/gailmcmbreakin.html
Even barrel manufacturers don't seem to agree. Some say yes: Kreiger, Lilja. Some say Kinda of: Bartlein Barrels"
http://www.bartleinbarrels.com/BreakInCleaning.htm
If you search google with "Barrel Break In Myths" - you get many pages, posts articles. If you search "Barrel Break In Procedure" you get many but most biased in the do it direction.
From what I have found, the break in procedures if done correctly (not damaging by improper cleaning) may make the copper easier to clean out during the break-in as you are cleaning as you go. Some say procedures help break the throat in faster as the copper isn't in the way. Others will say that not following the procedure will grind the copper into the barrel, damaging it or "fusing it" and all kind of stuff. But some say that not cleaning enough can grind the powder fowling into the barrel damaging it too. And certainly you can find those that will tell you that any solvent will eat away at the barrel a little too, damaging it.
You should do what helps you sleep best at night.
What I do: I clean the rifle well before I shoot it using a bore guide, one piece coated rod, careful of abrasives, I tent to push in one direction with patches and brushes unless using synthetic soft style, and clean if after each range session for the first 5 or so times keeping an eye on copper, accuracy and what the barrel is telling me. Then I only "clean" when accuracy is falling off or I arbitrarily think it time. Though for storage, especially when humid, if the firearm got wet or won't be shot for a while I will run a wet patch of oil down the bore (remembering to push a dry one through prior to shooting). This includes hunting rifles to full out custom long range rigs for me.
I have not yet seen actual scientific data of someone setting up an experiment using a scientific method on how a break-in procedure will help, doesn't matter or will hurt. That I would like to see.