I want to believe that. I really do. But I'm not sure that I agree. Testing of an app/system can, and does, happen within a non-real-world environment. I think it's kind of hard to justify that "testing the app" also requires the tester to physically drive to a restaurant/location, pick something up, and then physically deliver it to an end consumer. If this is the only way for an engineer to appropriately test a system there was a massive failure somewhere else. If it's not the only way to test, then it's hard to justify having the engineer do a job that a different person is typically paid to do.
"Building strong relationships with the rest of your team" may be a bit of a stretch since you're not doing a delivery with the rest of your team... you do it by yourself.
I'm not accusing DoorDash of acting in bad faith here. I'm concerned that this decision could unexpectedly put a portion of their employees in murky territory