Matt and Fred; I think I agree with you both.
In a perfect world, when two rubbing metal parts break-in to each other, it's generally asccepted as a good idea to keep them together, and not mix-match parts during a re-assembly, even if they all appear to be fine. This would apply to main bearings, pistons, and cams/lifters, etc.

However, that being said; the 103 rocker arm/cam rubbing interface seems pretty benign; (not like a small-block Chevy lifter, rotating in a bore, and spinning on the cam lobe).
I think you could mix/match a good rocker/lobe without much danger in the 103, i.e. put a new or good used cam in with good existing rockers. But, it's not the optimal situation for guaranteed longest life of the components.
kinda like installing new main bearings without turning the crank.

I suggested this approach for this application, due to the significant cost savings, but I definitely wouldn't recommend it if he was replacing the cam on, say, a 12-cylinder, 600 HP AMG that cost mega-bucks.

It's sorta the age-old Perfectionist vs the $$ compromise scenario.

Cheers,
DG