Article 390.7 and 390.8 seems to stress that the service fitting, sometimes called a 'doghouse' or a 'monument' is not a junction box where splices or taps can be made and that loop wiring is not considered a splice or tap. 390.8 continues to enforce that idea in stating that circuit conductors serving a discontinued outlet be removed such that no splices or re-insulated conductors (in the case of loop wiring) shall be allowed in the raceways.
The question is.... are the service fittings (doghouse or monument) considered a junction box by NEC or not. the extension of the question is can splices and taps and termination on binding post for the purpose of daisy chain to the next outlet in line be made in the service fitting.
There are several other code references such as pigtailing equipment ground, pigtailing neutral in multiwire circuits, cubic area of junction boxes, ground bonding etc that also seem relevant to this question in how to be NEC compliant in the wiring of outlets in this type of floor duct system.