Yep. That's what he said in the video - most serial killers have at least one paraphilia and 25% have the cross dressing one. We also know paraphilias cluster and escalate.
This is the first study he listed:
The Presumptive Role of Fantasy in Serial Homicide
Robert Alan Prentkey, Ph.D., Ann Wolbert Burgess, R.N., D.N.Sc., Frances Rokous, B.A., Austin Lee, Ph.D., Carol Hartman, R.N.,
D.N.Sc., Robert Ressler, M.S., and John Doglas, M.S.
https://www.researchgate.net/publication/20369367_The_presumptive_role_of_fantasy_in_serial_homicide
https://www.researchgate.net/profile/Robert-Prentky/publication/20369367_The_presumptive_role_of_fantasy_in_serial_homicide/links/54f9c1140cf29a9fbd7c521f/The-presumptive-role-of-fantasy-in-serial-homicide.pdf