@Excellent1 I would say that a single is probably the best for your son. I’m also an introvert (as is my D16) and what a lot of non-introverts don’t understand is that being an introvert does not mean we’re antisocial. It means that we draw our energy from having enough alone time to think and reflect. We enjoy socializing with people, but find that it tends to drain our energy. That’s completely different from the extroverts who tend to gain energy from interacting with others and feel drained or restless when alone.
If your introvert son is in a triple, he may have much less alone time to recharge his batteries. There will be plenty of opportunities for him to get involved in social activities that interest him.
It is precisely because I lean extrovert that I preferred having single rooms over situations where roommates shared the same sleeping/study space as myself.
Much easier to enforce self-imposed study/sleep hours on myself in a single rather than having to fight the desire to continue socializing/talking with roommates/hallmates who wander in until the wee hours of the morning. When I want to socialize AFTER the academics/part-time job obligations are done for the day…I can leave my door open or more often…go to where people gather in the form/on campus and hang out. No biggie.
Granted, I am not such an extreme extrovert that the loneliness aspect is a serious issue.