7's don't have enough velocity to justify 3/4 choke 6's or 5's do but I use 1/4 and 1/2 mostly.
I'm no expert but that doesnt sound right,
and anyway I didn't say it in the first place, I always go No. 6 for pigeons, I was just suggesting why he might have said it
IMO As long as your not using full choke or cylinder, and your shooting between 28g 7.5s and 32g 5s and your sensible about you and your guns limitations then you cant go wrong
im shooting 28g 7,1/2s through cylinder and dont have a problem