I am pretty sure that he's talking about a Tyco splice kit or equivelent.
The product is specifically listed as complying with 330.24(b)
B) Devices of Insulating Material.
Switch, outlet, and tap devices of insulating material shall be permitted to be used without boxes in exposed cable wiring and for rewiring in existing buildings where the cable is concealed and fished. Openings in such devices shall form a close fit around the outer covering of the cable, and the device shall fully enclose the part of the cable from which any part of the covering has been removed. Where connections to conductors are by binding-screw terminals, there shall be available as many terminals as conductors.
Since he doesn't meet the conditions of 330.24(b), they are not permissible in his case.
Edit: I don't like the idea of them even fished into place. The junction box with plate on the ceiling or accessible behind access door or false vent is superior, IMO. How do you find that splice hidden behind drywall if it fails ?
It's kind of a pay now or pay later, scenario.