Commentaries on tractati?

Can you write commentaries (+1 to authors base quality) on tractati?

The RAW in Covenants, p90 mention summae but there are numerous examples in Art & Academe (Averroes commentaries on Aristotle in the Appendix) that are commentaries on tractati.

Unless "commentary" is being used loosely in A&A...

Thanks,

Lachie