Yes, the reasoning for keeping your system all on the same leg in your panel is to keep it separate from potentially noisy appliances, which would be on the other leg. I haven't found any benefit from that in my system, but of course YMMV.
Why is it necessary to have gear on the same phase from electrical panel?
The source of power from any circuit is 120 V - therefore having some circuits on a different phase Side from the panel would seem OK.
It sounds nice to have everything on the same phase but does it really matter?
The only thing I can think of that would improve things is to keep all the noisy stuff on one side of the panel, like refrigerator, and the cleaner stuff on the other side.