When you refer to page 303 of the Envision owner's manual, I'm confused. On page 298, it doesn't specify any particular engine or drive train configuration when it explains how to "recreational tow" the vehicle. I take that to mean that any engine and either FWD or AWD can be dinghy towed.
It does give restrictions on dolly towing, however, as it pertains to FWD or AWD.
Are you looking at the current 2017 owner's manual? Recreational towing explanation starts on page 297 and ends on page 299.
PDF copy of 2017 Buick Envision owner's manual:
GO HERE
eta: My apologies. Please disregard both my posts as I'm a bit confused. I didn't catch the title of your thread. I assumed you were contemplating flat-towing an X1 or MINI which it kind of sounded in your post but maybe you were talking about using a dolly ...?? I would think a
FWD X1, MINI, or Envision would all be okay on a dolly but I'm just guessing.