Coupla Mono/poly questions

[Moho Disco]

When the Mono/poly first came out, its noise source
was a digital MM5837 chip.  Later, they switched to
a discrete analog circuit.  It has been suggested to me
that the reason they did this was because the MM5837
became rare.  It has also been suggested to me that 
the digital source was not "random" enough, so they
went with the discrete circuit to get a purer sound. 
My guess is the former, since I can't see Korg giving
a crap about whether their noise source sounded 
random enough... nonetheless, does anybody have
any other ideas why Korg might have done this?

Thanks,

Lava