But were the AAMC FL scores predictive of what you ultimately got on the real deal? The real exam experience differs from person to person (some find it harder, some find it easier, some find it about the same), but what's key is whether the AAMC essentially served as good representative practice on what you can expect on test day. And personally, I think it is even if the real exam is a lot harder (which is also true from my experience) because what's important is to understand how the AAMC test writers approached the passage and questions, and really nail down the test taking intuition.
For me, third party tests were a lot harder than AAMC FL tests by a mile (and apparently this was the case for many others). And pretty much harder than the real deal as well. So I'd agree that if we're comparing strictly on difficulties, going for something like NextStep would be better. But since AAMC writes the exam, it's key to understand the test taking reasoning from their perspective and not rely too heavily on third party reasoning.
This is why I viewed AAMC materials the best not because of their difficulty but because it's really important to nail down their thought process and reasoning that is important to doing well on test day. NS CARS is good for practice, as is TPRH CARS.
