Sorry I'm not following what you are saying.
Why the first Sophia's actual sex scene would be on PD19?
PD 15 has a lesbian scene and that involves Sophia by exclusion, as Ellie and Dylan, those who are involved in the list of scenes as per latest admission, will be not there (
no Dylan and
no Ellie events that day according to the intel) and the ranch event will be probably the only one event of the day ("
one large event...")
PD 16 has 2 hetero scenes and 1 lesbian. We have that old quote about the first extra-marital affair ("
something that nobody expected at the moment"), so I'd say that at least one of the hetero scene is for Sophia.
Am I missing something?