Imagine if ZBrush had a bug that broke being able to go up and down in subdivisions while sculpting without ruining your mesh. It would be practically unusable as software for sculpting.
Multires sculpting is probably one of the most foundationally important pieces of sculpting anything that’s even moderately complex. It’s almost as bad as box modeling without being able to undo. This alone makes any character artist I know immediately turn their back and walk away from sculpting in Blender over ZBrush, and (among other things) it’s greatly hurting more widespread professional adoption.
Really hope this is top priority for 2.82.