Inconsistent Header Behavior in `HttpServer.response.stream` Method

const headers = new Headers([['Content-Type', 'text/event-stream']]); // using the native Headers constructor here
const res = HttpServer.response.stream(myStream).pipe(HttpServer.response.setHeaders(headers))

const headers = HttpServer.headers.fromInput({ 'Content-Type': 'text/event-stream' });
const res = HttpServer.response.stream(myStream, { headers: headers })