Unfortunately, it is definitely is OEM.
My '03 X-10 had
the same garbage on it. Making the situation even worse is that not one of the first, second, third, and fourth fittings/hose after the thru-hull are a shut-off. It goes from a brass thru-hull to a 90* PVC elbow, to a plastic bard fitting adaptor, to a short piece of hose with a worm gear hose clamp on both end, to another barb fitting adaptor before you finally reach a shut-off, which is also PVC. Even if you remove the poor choice of materials, you are still left with a design that is inherently flawed as is leaves mutliple sources of potential failures before coming to the shut-off.
Oh yeah, and there is no shut off on the raw water intake for my engine either. I'll be addressing that this winter.
Not sure how MC got away with this, but it appears from what you are saying that somebody (whether customer complints, Coast Guard cracking down, or some other source) convinced them to pony up and do this properly. I still can't believe that given the option they skimped on something so basic, especially considering the amount of risk that could've been avoided for such a minimal additional cost relative to the overall build price of a boat. Don't get me wrong, I still love my boat, but this is yet another one of the many unfortunate flaws I found over time in areas that are typically out of sight, out of mind for most.