The article in-fact mentions exactly that :) Rational Systems’s “DOS/4GW” could make it seem to the programmer as if all of the machine’s memory

The article in-fact mentions exactly that :) Rational Systems’s “DOS/4GW” could make it seem to the programmer as if all of the machine’s memory was as effortlessly available as the first 640 K. DOS/4GW was included in the latest versions of what had heretofore been something of an also-ran in the compiler sweepstakes: the C compiler made by a small Canadian company known as Watcom. Carmack chose the Watcom compiler because of DOS/4GW;