I'm not saying I put more faith in opted practice scores because they are higher....... I'm saying I have more faith in them as an indicator than OAT Achiever simply because opted is very similar to the OAT and, most importantly, students scores on the opted practice test simply tend to be far closer to their actual OAT scores than their OAT Achiever scores are. Am I saying people shouldn't study with OAT Achiever??? No, however it is so clear to me that if someone wants to gauge their expected performance, that the opted test is far better than the OAT Achiever (as always I exclude the opted RC section). You yourself admitted that you were performing horribly on the OAT Achiever tests, yet did FAR better than that on your actual exam. I'm going to assume you took the opted practice test, right? Tell me if that score (assuming you took it relatively close to test day) didn't give a much more accurate indication as to what your actual scores are???
Secondly, I did many practice Kaplan tests to help prepare for my OAT. Were they ridiculously (not spelled rediculously) easy? I thought they were decent (not great, but decent) indicators of the actual OAT. They were close enough that if you think Kaplan is "ridiculously easy" than you should think the actual OAT is as well..... Would you honestly say the OAT is "ridiculously easy"? I was thoroughly prepared for my OAT and I didn't find it challenging as a result, but I'd never call it "ridiculously easy". I spent so much time learning that material in undergrad, and so much time studying it again in preparation for my OAT, that I understand how much total effort it takes to do well on that exam. I'll let my own scores speak for themselves.
I will conclude by saying that I do fully agree with you that students should try to challenge themselves when studying, so I have no problem with students wanting to use OAT Achiever, but again, with respect to accurately gauging expected exam performance, I feel that OAT Achiever isn't the best.