Good question. Other than "I just know SIC rating does not count for the real PIC type rating," not sure where to find it.
Just a stab at it, 61.63(d) spells out the type rating requirements, basically "alludes" to the practical test at the ATP level. 61.55 is where the SIC type rating stuff is listed, and, obviously falls well short of the full ATP requirements, as in the ACS and 61 Subpart G for ATP, 61.155(b), 61.156, 61.155(b), etc. but I really don't know exactly where or if the difference is written.