Luckily it's not too important for the 6080 since it is used as a cathode follower with slightly negative gain. I say luckily because balance was not really a quality criterion for these tubes and they can be rather grossly mismatched. I recall Svetlana having a devil of a time getting tubes with even a 25% difference between halves of the 6AS7 they sold. The 12AU7s will benefit from having balanced sections. But 25% difference in transconductance from side to side is probably fine. That is just an off the top of my head number, please don't use it to judge some tube vendor's credentials.
