I have a different perspective about the value of test prep for CASPer. First off, what is your basis for saying that you are 100% sure that no test prep would be even helpful for this test? If you're going off of what the takecasper.com people are saying, notice they don't even provide any references. They want you to simply go into the test unprepared and type the first thing that comes into your mind because it increases the validity of their sample size at YOUR expense. Keep in mind they say this is not a pass/fail test but rather one that "ranks" you but in my opinion, the effect is the same thing. If you rank poorly, then that's the same net effect as failing the test. In Canada where the test originated (like the MMI), it is worth as much as 32% of the pre-interview score and applicants there bust their butt off studying. The literature supports that behavioral based SJTs like CASPer do benefit from test preparation and coaching.
Congrats on getting in, but that could be due to fact that CASPer is probably not being weighed as much right now as it's still in the trial stages in the US.
However, I agree that it's sad that schools are starting to use this dumb test. It's BS and just another hurdle for pre-med applicants to jump through.
My two cents for applicants is to do at least one practice full length CASPer test so that you can at least experience what the test will feel like. It's only like $50 bucks so will not likely break you, but will give you an idea of where you stand relative to other applicants that have done the same test. I used Advisor Prep's CASPer tests last year and I found them to be spot on to my actual test in terms of the testing interface and content.
Personally, I think it's crazy that people walk into any standardized test without any preparation or the false idea that they can't prepare for it. Good luck to everyone having to take this test.