How does a solid roller cam act vs solid flat tappet

mini said
Wow 12.5 on pump 93... Maybe I should look at a different piston. I'm at 9.5 currently. Hmm

Now, I don't know how he figures that, because my dcr figures with 11.4:1 & that cam would be 180 cranking psi. But they firmly believe 200psi is what an aluminum head engine is supposed to be. I can't say I agree or disagree