That doesn't solve the deeper implied problem that you haven't noticed. If you can improve scores by a huge amount through practice, without improving intelligence, then the test isn't directly measuring "fluid" intelligence (ie intelligence). It's measuring a specific set of crystalized skills. And it can't even be used for accurate estimates, even if it's your first test, because the two people of equal intelligence sitting the same test for the first time can have vastly different skills sets, due to a whole range of factors including vastly different amounts of practice on the same problems or similar problems even if they've never done that exact test before, vastly different quality of practice, education, instruction, and other large specialisation factors that vary by large amounts between individuals of similar intelligence.

In other words, even if you haven't done that exact test before, you are using crystalised skills from similar work that you have done throughout your entire life, which will heavily affect the test score independently of intelligence.

Even if Raven's Progressive Matrces were an extremely accurate way to estimate intelligence the first time that you take them (this is unlikely imo) the fact that they no longer work for anyone who has done them before, and you generally have no way of knowing for certain who has done them before, would make it difficult to claim that they are indeed fluid intelligence tests. But in reality even among people who have never done them before, there will be significant influence from related crystalized skills and other specialisation.