Anthropic-LM v4-s3 (52B) is the model in question.
rlaif doesn't seem to be any less effective given the size of the model.
So base model+RLLLMF performs as well as base model+RLHF. That could mean a lot of things - it could mean the base model puts a ceiling on the total possible accuracy, so having human-level performance at the RL step doesn't matter as much. And looking at the scores on the individual tests that make up the composite accuracy metric, that looks probable.