MDS and oil?

I've read a bunch of posts - here, on Edmunds, and other forums - regarding the multi-displacement system and oil. But I haven't seen an explanation of how the two are related, even after searching, other than a passing mention that one of the criteria/data points in the MDS logic ladders might be the oil pressure. I've seen people advising for/against synthetics, etc. because "it's critical with MDS."

My questions: Does anyone have a definitive answer on how oil selection directly relates to the MDS? For example, if the dealer installs the wrong viscosity, how does the MDS "know" this? Is there a "viscosity sensor" somewhere related to the MDS?

I'm confused...