Maybe there not unbalanced. Maybe whoever wired the panel put appropriate loads on opposite power legs. AN example would be if you had two air conditioners you would wire those on opposing legs because chances are they both be on at the same time.
All of our AC and heaters were on one circuit and that was great since we did not use them all of the time - therefore we did not run that power cord when not needed.
Balanced or not is not the key issue just that you can supply sufficient amperage for what your intended usage is.