I cannot speak for other people or their methods,only my own.
This is how I break in barrels.
First I handlap a new barrel before firing it. Then,for the first 20-25 rounds fired,I clean in between every shot. After that,for the next 20-25 rounds,I clean after every 3 shots. After that,I consider the barrel "broke in".
I realize many people may think this is "overkill" however this is simply the method of breaking in a barrel I have formulated over 30+ years of experience.