Legal Advice,
Thanks for the help.
I think it would be most likely it is that FSP is full. If I was not competitive as an officer I don't think they would have sent me a OSB slot for ACO and JBAC. They obviously think I have the leadership skills and potential.
My medical was only just passed with provisional clearance for all my preferences. I am a DEO candidate so it may just mean flight screening was full for the year, which gives me peace of mind.