That's correct. The reason RuffCT/StringCT (two different names for the same thing) was put on the back burner is that only improves size but not CPU usage (still linearly related to the ring size with similar constant factors). So any large increase in ring size (the main reason for wanting it) would enormously increase processing load. At small ring sizes, there isn't much improvement in size.

This is in contract with bulletproofs which not only reduce transaction size but also appear (in early tests) to also improve processing time a bit. So that is a clear improvement and the top priority at the moment in terms of improving the efficiency of the blockchain.