More Questions about Dedicated Circuits

I had an electrician install a 60 amp subpanel in my garage, which is below my audio room. I am having him install 4 circuits to the audio room, (2)20 amp and (2)15 amp.

I told him that all 4 circuits need to be all on the same phase(leg) of the panel. He seems reluctant to do it, saying that it would put things out of balance and cause problems, etc. I tried to explain to him that I'm told (here on A-Gon) that it is better for the audio system, but I am not able to explain why. There will be no other circuits in the panel.

My first question is, will 4 circuits on one side of the subpanel and no circuits on the other side of the subpanel cause any problems. Does anyone else have it set-up this way?

My second question is, why is it a problem to split the circuits, 2 to each side of the subpanel?

My electrician is coming back to wire this up this Wednesday 4/28. Any assistance is appreciated.

Thanks,
Rick