This seems comically complex and wasteful compared to the extremely old fashioned "restaurant hires person with a bike" solution.
Capitalism does not optimize for sustainable global maxima, only local ones - and in this case, the incentives aligned for this to be a local maxima.
They know that the path finding algorithm isn't the important part right now. The most important thing is proving that the robots can provide the service.
These types of path finding algorithms already exist, so it's just a matter of automating and improving margins.