Or does the SIM instead "use" only hr/9 as a kind of overall shorthand for opposing batter power?  I ask since I am sometimes surprised by what SIM doesn't know (and I).  And I don't notice .ops in pitcher advanced stats...

The lower the ERA, hits allowed and HR allowed are, the better they will do at limiting extra base hits.

http://www.whatifsports.com/devchat/devchat.asp?chatid=65

I thought that one of the updates in the past few years eliminated ERA as a factor of 2B/3B rates. While a pitchers OAV will play a factor in hits allowed obviously, 2B/3B were determined solely by the hitter (and park and normalization obv.). I was never sure if pitchers with good hr/9 rates and/or negative homerun parks would turn those homeruns in to outs or 2B/3B or some combination of both...