There is Uber Eats, Freight, and JUMP bikes in addition to their ride-hailing product. I believe they share some technical similarities but still each of the four(I know of) are startups ideas imho.(See Lime, Lyft, Sennder, Delivery Hero, Takeaway.com, door dash etc.)
Agreed, I'm curious what they are actually working on with a team like that. Although they do have a not unsubstantial physical data center presence so I think a fair number of engineers are in support of that and not software engineers.
I read that they had 2,000 engineers out of 6,000 employees in 2016, though I don't know the numbers now. That seems gigantic.