During the discourse with Senator Hatch, didn't Roberts also agree that Casey modified Roe in such as way as to alter the original holding? That included dumping the trimester nonsense and using "liberty" as the rationale for the ruling, rather than privacy. To me, that sounded as if Roberts was agreeing with Hatch that Casey itself proved that Roe isn't sacrosanct. And, of course, it shouldn't be, as it's a hideously unconstitutional ruling.
I didn't hear that exchange, but if you remember it correctly, it seems that Casey is more vulnerable than Roe, in Roberts' mind. It certainly should be.