Well I for one, think what Mass DOT is doing here is a bad practice. It counter-intuitive, illogical and potentially confusing to drivers. I couldn't say for sure whether it's MUTCD compliant or not, but I'd sure like to see an FHWA opinion on this issue.
Also, just a point of info: The sign-spreading concept in the Manual is only a recommendation, not a standard. All the instructions say should, not shall. So even if Massachusetts is mis-applying the concept, I'm not sure it matters since sign-spreading is not required.