If you were forecasting how this company in particular would deal with a downturn, it's a reasonable guess that they'll try to do the same thing to their own workforce, if they can find engineers willing to take on gig work. It's in their DNA.
To be charitable, the grandfather comment is a warning to think about the broader effects of the work we do, driven home by the possibility of a "what goes around comes around" situation.
EDIT: as many have pointed out, taxi drivers don't get benefits either (I originally said one of the margins Uber competes on is not providing benefits).