According to GM, the reason some 2018 Equinox models cannot be flat towed is NOT due to switchable all wheel drive, but because of the final drive ratios of the rear axle.
It’s important to note that the owners manual specifies that only these three 2018 Equinox vehicles can be recreationally towed four wheels down:
Front-wheel-drive, 1.5-liter gas-powered.
Front-wheel-drive, 1.6-liter diesel-powered.
All-wheel-drive, 1.6-liter diesel-powered.
GM officials say that because the electrical architecture in the 2018 Equinox differs from 2010-2017 models, it is not necessary to pull any fuses in the 2018 Equinox. However, just as with 2010-2017 models, a charger will be necessary to keep the towed vehicle’s battery charged. The current owners manual for the 2018 Equinox will be revised to reflect the need for a charger.
Also, I'm told there is no lockout on the steering wheel for 2018 Equinox models that can be flat towed.