In Color Treatment mode, when an image has at least one Graduated or Radial Filter local adjustment, then activating the TAT on the HSL/Color panel results in Convert to Black & White No being added to the History panel.
In Black & White Treatment mode, when an image has at least one Graduated or Radial Filter local adjusted, then activating the TAT on the B & W panel results in Convert to Black & White Yes being added to the History panel.
This problem does not occur when there are no Graduated or Radial Filter local adjustments, nor does it occur when the only local adjustments are Local Brush Adjustments.
These are meaningless steps being inserted into the History panel every time the HSL/Color or B & W TAT is activated after a Graduated or Radial Filter has been added.
Yet another annoying new bug in LrC 9.3 for which I use Undo to remove from the History panel every time it occurs.