They all do this now, to one degree or another. [1] [2]
The economics are even worse (because they don't get a cut from the restaurant), so these types of orders are either very high fee for the consumer, a loss leader, or both.
[1] https://gizmodo.com/doordash-pizza-arbitrage-shows-the-fubar...
[2] https://www.eater.com/2019/10/30/20940107/grubhub-to-add-res...