These guys are not kosher. Building code allows metal electrical boxes of all kinds (telephone, FA, and power), up to 100 square inches per 100 square feet of wall. Any one box has to be no more than 16 square inches, and boxes on opposite sides have to be separated horizontally by 24 inches.The exception is for putty packs or boxing with sheetrock.
Plastic boxes have listings based on the manufacturer. I saw some advertised that allow back to back boxes.
To allow telephone off the hook (lol) but not power boxes is simply a misunderstanding of the codes.
As for the electrical inspector bowing to the building inspector; he works for the guy. Not too many folks will contradict their boss in public.
The UL listing details this, as does the IBC:
"711.3.2 Membrane penetrations.
Membrane penetrations shall comply with Section 711.3.1. Where walls and partitions are required to have a minimum 1-hour fire-resistance rating, recessed fixtures shall be installed such that the required fire resistance will not be reduced.
1. Steel electrical boxes that do not exceed 16 square inches (0.0103 m2) in area provided the total area of such openings does not exceed 100 square inches (0.0645 m2) for any 100 square feet (9.29 m2) of wall area. Outlet boxes on opposite sides of the wall shall be separated as follows:
1.1. By a horizontal distance of not less than 24 inches (610 mm);
1.2. By a horizontal distance of not less than the depth of the wall cavity where the wall cavity is filled with
cellulose loose-fill or mineral fiber insulation;
1.3. By solid fire-blocking in accordance with Section 716.2.1; or
1.4. By other listed materials and methods.
2. Membrane penetrations for listed electrical outlet boxes of any material are permitted provided such boxes have been tested for use in fire-resistance-rated assemblies and are installed in accordance with the instructions included in the listing.
3. The annular space created by the penetration of a fire sprinkler provided it is covered by a metal escutcheon plate."