If someone discards town and they got scum, scum, town
Then they're scum
If someone discards town and they got scum, town, town
Then they are either scum or they used the scum role with town alignment
But then why did they use the scum role, have you seen the set of scum roles? Most of them suck. It's most likely that they kept the scum card for its alignment and paired it with a strong town role.
The probability of triple town is only 18%
But there are way more than just 18% of the list with town discards. Meaning we have a ton of scum in those people that discarded town