I've pulled a MWBC into the crawlspace of my house, with one phase supplying outdoor GFCI receptacles and the other phase supplying nothing so far. The conductors are enclosed in a combination of all-metal conduit, MC cable, and metal junction boxes throughout.
I am thinking of using the unused phase to supply would-be new receptacles in bedrooms. This would be MC cable to metal boxes. For reasons of geometry and convenience, I'd like to split the unused phase at the junction box shown in the drawing below, with one leg running to Bedroom 1 and one leg running to Bedroom 2. This is a grossly simplified drawing; the bedrooms are not next to each other.
The question is whether installing a listed AFCI receptacle at the first outlet of each split in the branch as drawn is sufficient to meet 210.12(A)(5). Where I get tripped up is in the reading of "first outlet", as I have multiple first outlets in my plan.
210.12(A)(5) If [...] Type MC cable [...] , with metal boxes, metal conduit bodies, and metal enclosures are installed for the portion of the branch circuit between the branch-circuit overcurrent device and the first outlet, it shall be permitted to install a listed outlet branch-circuit-type AFCI at the first outlet to provide protection for the remaining portion of the branch circuit
I anticipate the community recommending the installation of an AFCI breaker, and in my panel this is possible as GE AFCI breakers can support MWBC's. However I'm nevertheless interested in an answer/solution in the context of 210.12(A)(5) specifically.
Ground wire isn't shown above, but it's there.
edit: misspelled a word edit2: updated picture to show junction box inside crawlspace opposite exterior GFCI receptacle