I dunno Harry.
The question would be if it was a military or civilian project. If the latter, the Army generally finished what they started. Even if, perhaps especially if, it was a rather silly thing to do in the first place (Antonine Wall anyone?). Besides, what would motivate the Army to do this, they had a perfectly nice fort already.
As to the civilians doing this, well, the quality of the finished stonework seems suspiciously good for late vicus work. I know Site B has been bashed about a good deal, but most of what we have been scraping around at under the watchful eye of Justin appears to be the kind of work homeowners might do on their day off....after a few pints of fermented liquids!
I suspect it will be an annex of an earlier military project. Side walls later robbed out as being in the way?
Where is that coin when you need it? Another argument against the late vicus theory, at that point cruddy pot metal radii were just about worthless and most roman sites of that era are awash in them.