@drevinum9It doesn't need to be accurate. It detects trends. Thus the 30 second interval. The more often you are found away from your team, the more you "trend" to be solo. There is nothing to "follow" as far as rules go. It just examines your play style and fits you with teammates that have similar styles.
If your team is slow and you abandon them, then you should be treated as abandoning them, regardless of why.
It can detect AFK and treat those differently - put those with players that trend AFK in the next match as well.
We could incorporate this trend into matching where players can choose to have skill the dominate match factor, or the abandonment trend the dominate match factor. I would choose the latter because I don't care as much about my teammate's skills. I just want to play with a team... a real team. And I think there are people that would agree with me, teammates that abandon them makes the game far less enjoyable than teammates of lower skills.