Yes, steep turns were once in the Instrument Rating - Airplane PTS and were removed with the introduction of the ACS.
They remain in the current Flight Instructor - Instrument Airplane PTS. This is a lack of harmonization which has been addressed in the forthcoming Flight Instructor - Instrument Airplane ACS, which has been "finished" for some time now but not available yet due to issues being hashed out between the DOT and FAA. In short, the DOT
issued this memo in December of 2018 which expands the internal processes necessary for the FAA to issue new guidance documents, including review by the FAA Chief Counsel and (now) the DOT’s Office of the General Counsel. If deemed "significant" as a guidance document it may also require review by the DOT's Office of the General Counsel’s Office of Regulation and even the DOT Secretary him/herself. This has significantly slowed the progress of the ACS rollout and affects revisions to the ACS as well.
So, you're probably going to see steep turns wink out of existence as soon as the FI-IA ACS rolls out, and we don't know quite when that will happen.