Chris,
The instructions on the website are correct:
Wrestlers only need to weigh-in one time for all three styles provided he/she actively competes in the first two styles. Athletes that wrestle in the first and third style must reweigh-in for the third style.
To phrase it a little differently, once you've weighed in, that weight is valid for any subsequent styles as long as you compete in each style. If you do not wrestle one style, you'll need to weigh in again for the next style.
