Read the article, this isn't talking about consumer-owned vehicles but the Cruise Origin robo-taxi service. They're small autonomous shuttle-style cars.
Basically GM reinvented the bus but made it smaller.
So to answer "How does it park at Walmart" - it takes the passenger to the front and drops them off then continues on its way. I believe the intent/current trials using Bolts have an app similar to Uber, you put in your current location + destination, then it comes and gets you, then drops you off.
Almost 0 value in removing a steering wheel or any kind of input to a consumer-owned car like that, makes some amount of sense for robo-taxis. (They specifically wanted passengers sharing the ride to face eachother to ease safety concerns, and they probably don't want random Joe getting up at the emergency controls and driving it off road)