It’s not that you have to change the UCA, it will go together fine. The upper control arm, more specifically the upper ball joint, can’t handle the extra lift, it puts it on a harsh angle. You need an aftermarket UCA with more forgiving geometry at the ball joint.
As far as shocks, some kits just get there differently like using a new spring/shock/strut/etc. Not all leveling kits are just spacers.