It partly is 5-4, ACB joined part of the dissent on several of the more egregious issues. But at the same time, if RBG's seat had stayed Dem ACB wouldn't be there and it's a wash.
(Some other bad cases would've come out 5-4 the other way though)
Right now, I'm supposed to be mad at the woman who...had she retired in 2013, not changed the immunity decision at all because it would have been 5-4 without ACB? That's quite the statement about one's priorities.