It’s hard to imagine something easier and more reproducible for developers than connecting to localhost and having your request routed to the correct endpoint automatically, whether you’re on a disconnected laptop or in production. That’s the power of the ambassador pattern, which Envoy enables.
When the request is routed correctly, yes, but the question is when it's routed incorrectly (perhaps because information you're providing to Istio is incorrect but you haven't realized it yet, perhaps because of bugs in Istio).