Question about Lifter Oil Gallery Plugs

I've been told, FWIW, that not all thrust plates are machined on the back side... As I said, FWIW... A friend with a lot more experience than I said the plugs were for the non machined thrust plate.
I've only had a couple of 'em apart, and seen with and without, and no I haven't seen the un-machined thrust plate.
That and $2 will get ya a large coffee...