All that being said, how come a passive array like spy-1d has multiple emitters? They wrote each array has 8 of them. What do those emitters do? What is their purpose? Are they involved with providing midcourse updates?

I have to confess I’m not to deep into SPY-1, but every phased array radar (also PESA) has multiple emitters. In case of PESA they are only driven by on single central wave generator and don’t generate the wave itself like AESA.
So I could imagine that SPY has propably more than one wave generator to group different emitters of the array for different tasks.