Sorry, I know how we hate this topic...But......(MA. On the 2008)

Same 2- family, 210.12(B).

"Hallways" are listed. Would I need an ARC fault for the new proposed ckt? It's a 'common' area. not technically "IN" the dwelling "Unit".

Nope. At least as I see it ... the 'entry' they refer to seems to be inside the unit.

Don't feel bad; they forgot stairwells too