SSL'd SMTP is a non-standard extension that nobody uses. (In fact, the port assignment for it was revoked in 1999!) TLS on port 25 is how you do secure email (mostly so you can advertise AUTH PLAIN safely.)
I think there are probably some MTAs that will STARTTLS for normal SMTP connections, but again, I've never heard of anyone using SSL/TLS as a spam-filtering criterion. (I might look through my old logs to see if anyone other than me ever issued STARTTLS on my mail server. But I'm guessing the number was near zero.)
In any case, from a decade of listening to the random things he's had to deal with, I certainly have to agree with your final comment.