Json Server NOT working with oauth authentication

I'm using the "official" 6.x-2.0-alpha2 with OAuth authentication.
The problem is in json_server_server() function (line 46), where "method" is unset from $_POST. OAuth authentication on the client calculates a signature on all parameters sent to the server (i.e. method included) and when server do the same it gives an error because signature is different because the "method" is missing.
I simply commented out the line, but I'm wondering if there is any reason in unsetting the "method" parameter from $_POST...