The orbs influence subweapons, not the VK.
Where's the evidence that the VK is powered up by the orbs in LOI specifically?
Julius' run doesn't supersede anything which constitutes a main run in another game imo.
Correct me if I'm wrong, but orbs are dropped by bosses, the same way that they are in the original CV. The required orbs also open the path to Pagoda.
Sara's sacrifice alone is what triggers the Whip of Alchemy into becoming the VK, as in it physically changes and starts radiating a purple hue.