Anselm and Aquinas on Satisfaction

Anselm is famous for giving the first detailed explanation of the Satisfaction theory of the atonement around 1100AD. The Satisfaction model eventually developed into Penal Substitution, and there are many similarities. Basically Satisfaction sets the atonement against a backdrop of the medieval feudal system, while Penal Substitution moves these ideas into a law-court setting. Anselm's work represents the first time in church history that any ideas close to penal substitution are explained and defended systematically in any level of detail.

Of course, purists would say Satisfaction is not Penal Substitution, since there are some differences, some reasonably significant. eg in Satisfaction Christ doesn't really have to suffer, only be perfectly obedient to God's will - God only wants some form (any form) of reparations made for sin, he has no particularly desire that there be punishment or suffering. As a result, Satisfaction tends to be considered slightly less theologically offensive than PS by those who object to the idea of a God who demands suffering. (In fact, for Steve Chalke, it seems to be this difference that makes him think Satisfaction is okay and penal substitution is "cosmic child abuse") Often therefore, despite their similarities, PS and Satisfaction are treated as different models of the atonement. But given that the authors of Pierced for our Transgressions managed to mistake even Ransom from Satan for Penal Substitution I was extremely surprised not to see Anselm on their list of teachers of Penal Substitution.

I see on their website they say:

Anselm did not teach penal substitution... Thus his omission from our list of those who have endorsed penal substitution was not accidental.

I can accept that view as valid, certainly. That was my thought when I read their book and saw they'd left out Anselm. I was particularly mystified however when I saw they'd put Thomas Aquinas in their list and quoted him teaching the Satisfaction model... they called it Penal Substitution. In their quote of him, Aquinas even uses the word "Satisfaction". So if they are really so awake to the fact that Anselm's Satisfaction model is not PS then why could they not spot Aquinas teaching Satisfaction when he specifically says he is? Elsewhere in their book they cite Eleanor Stump's article on Aquinas' Satisfaction doctrine... if they had read that article they would know Aquinas teaches Satisfaction and what he means by this. So again, I just can't fathom what was going through their heads in including Aquinas but not Anselm in their list of PS supporters.