Not all professional organizations have the same 2 year rule. Some have a 5 year rule. Some have a never rule. And some don't have a set time limit but instead are asked to use their judgment. So you would need to know what organization this T follows the guidelines for. Also, my understanding of the 2 year rule is that it is not just dating, but there is to be no contact during the 2 years before the former T and client can begin dating. So you can't be friends for 2 years and then start dating and be in compliance with that particular rule.

My guess is an intern would want to follow the guidelines of the profession he is aspiring to. So if he will be a Licensed Marriage and Family Therapist, he would go by the guidelines of the AAMFT. If he will be a licensed Psychologist, he would go by the APA guidelines. If he will be a licensed mental health counselor, he would go by the AMHCA guidelines. Etc. State guidelines can also play a role.

ETA: I looked in the AMHCA guidelines and it says:
"Students and supervisees have the same ethical obligations to clients as those required of Mental Health Counselors."