"The gain and loss of this spiritual quality [grace] are real changes in a person."
"Scotus argues, first, that a change from injustice to justification can only occur if God brings about a real change in the sinner."
I haven't had much time lately to work on this, and will have less in the future so i'll post it anyway. I skimmed through the Scotus and it seems that Cross is accurate here. At least, Scotus does posit that the infusion of grace is a real change, while the accompanying remission of sins is distinguishable only by reason, ie., a distinction of reason. From the four arguments Scotus makes at the beginning of the question it seems as if this is due to his use of Aristotle. Grace is a form in the will. sin corrupts this form in a real change. In the sacrament of penance, grace is infused again, in a real change. As sin seems to be a privation of grace (this would bear further investigation; I didn't see this spelled out explictly by Scotus), it cannot be corrupted by a real change like grace can. Privations aren't forms in the category of quality.
That's it for now. As for Cross, he seems to have all the right pieces, but hides the bit about grace at the end of one paragraph, and then spends the next two pages emphasizing the remission of sin without a real change. The net result is to make Scotus sound like a proto-protestant if one has missed the bit about grace. It is somewhat distorted and I do not know why Cross put it that way. But he had a lot on his plate in that book and so perhaps can be forgiven. The question would bear more looking into, however, as this is a long question in Scotus, with even lengthier commentary by the 16th century scotist. Trent is mentioned left, right, and center. But, it does not seem to be relevant to the issue at hand, ie, did Trent censure this alleged protestant teaching of the subtle doctor. The answer is no. The Council wasn't looking to settle longstanding scholastic disputes.