I've noticed various contracts played out weirdly.
For one application (can't remember what) kyb is the oem shock supplier. However they are not allowed to disclose info or sell to anyone but the dealer. So your stuck.
Monroe is the oem for the s60r struts. They are allowed to disclose to some extent, so you see them on rockauto. Same exact product as dealer but for half price.
Sometimes these oem suppliers also supply the aftermarket. Like Kevin said, you don't know if they are allowed to disclose these specs. If they can,it's obviously cheaper to keep production running then to retool. Hence I'll open a beck arnley or napa box and sometimes find oem.

For example (I don't know who makes shocks for ford, just a hypothetical example). Kyb might have the ford contract, so They make a high spec shock for the Taurus. However due to contract issues they can't disclose, so they sell a similar shock under their brand name. Its no longer an oem spec part, but still decent quality. They in turn also supply fords budget motorcraft line, but have to meet a target price, so They outsource and make a crap shock. All three are made by the oem, two are sold at the dealer, but only one is oem spec. Weird.

I would never trust a parts seller for advice. Kevin, however,is in the know.