I can’t speak for sure but that’s a little unlikely. RSUs are taxed on vesting. Bad idea when employees can’t sell a portion of it to pay the tax.
Uber, Airbnb and the rest definitely give RSUs. Details may vary but they may use contracts like “double trigger vesting” where you don’t actually receive the shares until they’re publicly traded.
Still, Uber employees will be happy that they can finally sell those RSU awards (in six months when the lockup expires).