... and magically breaking 10 years of web applications is also a big MUST NOT. Why else would the spec itself dedicate an entire paragraph and add two response codes just for legacy cases? The article, if you read it, also explains why. All old browsers map POST so they stuck to that for forms and XHR's broader capabilities map to the standard when possible. That's a pretty good argument, unless you have better ideas, again, make your suggestions heard.