AFCI devices are not going to object to that Yankee's ingenious 'solution' for there is no arc faulting failure.
The problem with that particular install is that there is no suitable OCPD up the line. Consequently, there'd be no logical reason why one could not overload the conductors, melt through the insulation so quickly that a flame started before even an AFCI tripped.
If the short is SMOOTH and regular, the logic of an AFCI is going to see the cook off as merely a 'hot plate' pure resistance load.
AFCI are going to object to universal motors much more readily -- the commutator -- of course.
One simply can NOT use conductors undersized versus OCPD -- unless the tap rules are obeyed.
Beyond that, as previously commented, the slack installation is not going to stay tight under use. Of all the flaws I've witnessed in installations -- loose EMT, boxes, fittings come at the TOP of the list for hazard. They are the source of rubbed conductors and frayed terminations. When not correctly bonded, they are the source of electrocutions. They happen ALL the time -- typically killing a kid so young as to not recognize that something's gone amiss with the electrical system.
Beyond that, the trade, generally, does NOT favor DIY kludge-ups -- if only for economic reasons. With knowledge comes realization: the DIY crowd is dancing with death -- and dares not know it.
Lousy DIY plumbing attempts reveal themselves as drips and ugly noises. No-one dies.
Lousy DIY electrical installations are not apparent to most -- and the perils include loss of structure and loss of life.
Add to that the commonplace DIY attempt to work on hot circuits! DIY are willing to take chances that no experienced hand would tollerate.