Here is a link to a discussion under the Must Read page, other discussions on the topic have taken place on the forum as well for more info...
http://club.alembic.com/index.php?topic=309.0
That was an engaging read, thanks...although it still didn't really answer the question!

Lots of conjecture, a couple anecdotal "It seems this way to me" posts,
one post that started to get at the heat of the matter (dfung60's from June 27, 2016, 10:11:59 AM), but nothing definitive.
I do get how the inclusion of a Master Volume Control
in addition to two separate pickup Volume Controls makes those two discrete controls more
useful...and I could
almost agree that in that configuration there
might be more timbral combinations available than simply having a single Master Volume Control plus one pickup Balance control. Almost...
But in an active circuit with low impedance pickups, why would there be
any timbral difference -- not volume difference, just tone -- between, say, Neck pickup at 90% and bridge pickup at 40%, versus the Balance knob skewed N% towards the neck pickup? (Sorry, I realize this is a math question and so perhaps solving for N might answer that question...maybe?)
Thanks.