I am by far an expert in this method of fruit growing but in my opinion it is a very intelligent way to maximize a small space and keep fruit trees in check. 
Dave wilson nursery and Tom spellman have some wonderful videos on how to prune and layout a backyard orchard. 
https://www.youtube.com/user/DaveWilsonTrees

I have 3 peaches in a row on 4' centers, 3 plum in a row on 4' centers and 3 apples on 8'. None will ever be more than about 7-7 1/2 feet tall. 
I hope to add 3-4 more peaches a couple plum and a few apples this year. May not happen that quick though.
this was taken last april. those are my citrus in the pots.