48 hour rule

Is someone able to clarify the 48-hour rule for me? I am under the impression that only the SOC is required to be completed within 48 hours of referral, return home, or physician ordered SOC date. I am being told that ALL disciplines (PT, OT, SLP, etc) are required to go out within 48 hours if on the initial referral. I have reviewed the CoPs and the interpretive guidelines provided by CMS and it does not state anywhere that ALL ordered disciplines are required to go out within 48 hours.