Of course you can achieve any ratio of the pickups related to 100%. But 50/50 is probably not the same as to get 100% out of both pickups !
Common balance pots provide the following characteristics:
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In centre detent both ways are slightly attenuated, because the resistors in the stacked pot are effective through the whole turn ! Due to the log curve it is not 50%/50% obviously, but not 100%/100% either. Although it is 50/50 as a ratio...
To achieve a zero attenuation in the centre position you need special balance pots which are effective only on HALF of the turn. Then you can get full signal out of both pickups - as with a VOL/VOL combo.
As far as I know Joey/Mike use these special pots for the Pope pre, is that true ?