We all agree that there must be a box there .
What we are debating is the installation of the receptacle. Correct?
406.5 Receptacle Mounting.
(A) Boxes That Are Set Back. Receptacles mounted in boxes that are set back from the finished surface as permitted in 314.20 shall be installed such that the mounting yoke or strap of the receptacle is held rigidly at the finished surface.
314.20 In Wall or Ceiling. In walls or ceilings with a surface of concrete, tile, gypsum, plaster, or other noncombustible material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1?4 in.).
Now if you think it is:
(B) Boxes That Are Flush. Receptacles mounted in boxes that are flush with the finished surface or project therefrom
shall be installed such that the mounting yoke or strap of the receptacle is held rigidly against the box or box cover.
Both have to be accessible
See post 15
Accessible (as applied to wiring methods). Capable of
being removed or exposed without damaging the building
structure or finish or not permanently closed in by the structure
or finish of the building.