I don’t know about the idea of CR being harder to raise…
When I was a sophomore I had like a 60 or something on CR (had always been my worst standardized test section by far) and the next year I somehow jumped to a 79 on CR for the PSAT (which ended up being what made me a national merit semifinalist) and a perfect score on the ACT’s reading section without really studying that section specifically at all.
I mean I know that my experience is really rare and all, but it definitely goes to show that CR can be improved very quickly.