There are benefits to combining all the household's UR points to one designated, highest redemption value card because the person doing the redemption will have all the points at their disposal to book a single or several itineraries and/or make larger redemptions through the UR Portal. If transferring UR points to travel partners instead, transfers are made in 1,000 point increments; so if Player 1 has 1,250 UR on his account and Player 2 has 1,900 UR on her account, keeping the two stashes separate means the household can only transfer 2,000 UR, but combine them and you can transfer 3,000 UR.
So relatedly, even if
@Calfan can't transfer UR from CIP to CSR, yes, she could use her CIP to transfer UR to UA at 1:1. Not being able to combine points between the two cards might mean that she has some leftover points >1,000 increment on the CIP that can't combine with the balance on the CSR.
I don't know if these possible changes kills the benefit of 2-player mode in chasing UR bonuses, because each player can still make separate redemptions and transfers, but it might sap some value from the margins.