I think it's fine to split off separate named areas (from unnamed areas), as you have.

MCP, RdG and CO are individual things (now) and so should be tagged accurately "for what they are, as they are."  That can be like nailing up jello.  You, or somebody, or you-interpreting-CPAD or something like that must know something about these in order to properly enter them into OSM.

That includes the (complex) history of how such tagging both emerges and remains fluid.  So, we are now having a "what do you know about these places and how do you wish to tag them" discussion.

Whether something even has leisure=nature_reserve tag applied can be a long/messy discussion I'd like to avoid.  It is true that this tag is associated with places that people can (easily) go to so we can, say, "observe nature" from a trail, platform, parking lot, or maybe take a hike if we stay on the trail.  If you know those places are like that, tag them so, perhaps with a bit more micromapping (a parking node, a trail...).