I got it to work by setting the constraint for the Drawing # to "right" - or deselecting both the L & R boxes. The text alignment setting - left , right , or center - doesn't seem to do anything - i still get the Drawing # and Sheet # blocks holding their right edges.
Anything I do to get those two aligning on the left, or to get the line and the Drawing # aligned to the left [if i don't have a sheet # text block] results in the scale and Title text blocks out of alignment.
"Wrapped text" was already unselected in all cases.
The result i now get is acceptable - but still not ideal.
I still think the v.2020 Drawing Label tool was far superior in ease of use and drawing editing time performance.