I don't think much of the "Slave Training" is complete.
As you said, removing Sarina's or a male slave's penis only has a small change in the dialogue "Lets test out that pussy", or something, but the pictures remain the same. Starting to call a male slave by the female pronouns doesn't change a thing (and you have the option again after doing it). MSC doses just tell the subject to relax and enjoy it. BmB raise sex drive, and stops them from talking coherently. TFM doses don't seem to do anything at all. CMD doses don't even appear. If the various trainings (inspect, masturbate, oral, fuck) have any cumulative effect after repeated use, you don't get a progress bar
And, as you pointed out, surgery doesn't change them from "female/male/trans".