I don't know the answer to that. You've mentioned this before, but I simply don't recall the 1991 redistricting becoming effective in 1996.
My best guess to that question is that the redistricting becomes effective once it passes Justice Dept scrutiny, and then it's subject to challenge in the courts. In the meantime, the new district boundaries stand.
You maybe correct about the plan being implemented awaiting final disposition in the courts... Some of that seemed to have happened in the 1990 cases.....