MG,
Not true - you can express your intentions to join any particular ac type at any stage of trg or selection - you even get a space on your paperwork to rank your preferences (FJ/RW/ME).
Very few failed FJ mates end up on rotary - if they've failed FJ they probably wouldn't fair much better on the SH force. Most of them get dumped on the AT fleet!!
(at least that's how it was when I joined / went through trg many moons ago - the goalposts are never static).
Besides, being a 'failed' FJ mate means you have not met (usually by a narrow margin) what is arguably the highest standard required in the aviation world, anywhere in the world. Nothing to be TOO ashamed of..........