Yep, anyone who wants to try for the PJ's has to be in the AF already. They do not take new enlistee's directly. Although during AF basic there are orientations/recruiting for the PJ's. They do accelerate you thru AF basic if your prior service and make the initial selection for something like PJ's. Especially is you have skills that they a feel are attributable.
But you do have ETS before they will allow you to sign up for the AF. You might be able to get a RES/NG slot directly for the PJ's. But AD slots are filled by active duty personnel.
Very few are filled by boots from basic. Most come as a cross-training opportunity.
Although my experience there is a little dated since I have been out since 95.