When the browser-kit Client follows a 302 or 303 redirect, the request is with the GET method name in lower-case. The http 1.1 definition defines the method names as case-sensitive.

Where the method name is set to 'get' instead of 'GET':
https://github.com/symfony/symfony/blob/master/src/Symfony/Component/BrowserKit/Client.php#L478

The relevant section in the HTTP protocol.
https://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5.1.1