Yes. Just repeated the steps above with a new application from scratch. First parameter is always blank. Changing order of parameters in Web request changes which is blank.
If you look at the URL once the application is running, the first parameter is not shown. For example, when submitting ...&A=1&B=2&C=3 the application opens and the URL contains ...&B=2&C=3&appId=... The fields of course are also not populated.