It seems like it logically would, but I cannot find spec support for that: https://fetch.spec.whatwg.org/#concept-http-network-fetch

Wait until all the headers are transmitted or fetch is being terminated with reason reason. If fetch is being terminated, then set response’s termination reason to reason.

After that we jump to step 5 and start doing stream body stuff, which will eventually land at "If at any point fetch is terminated with reason reason, run these subsubsteps:". So I guess it would fulfill with a stream that's errored? But how would you even know what status code to use?

Similarly, what if a network error occurs during the header transmission? I can't figure that out either.