Dave - Agreed, I am very much used to Class 3 PCBs, so I immediately notice when etchback is not present.  I did look at the image in more depth after my initial email and noticed that there is a straight wall with evidence of voiding and irregular plating behind the wall.  So it looks like the desmear step was poor at best.  Normally I would send this to ST&S (Gerard O'Brien) for a professional look (I know PCBs well enough to be dangerous but not always correct).

The desmear doesn't look very good.  This may be a point of contention, but is the first concern,
The second concern is as you stated, is etchback required, if so, then this is hard failure mode.