I agree with this up to a point, but I would also add that for sciences, if you have a really good memory and decent maths skills, I think it is possible to get a 9 at GCSE through rote memorisation. In theory, you have to apply your knowledge, and evaluate things, but especially for the evaluation questions, you can learn the evaluation points off by heart, and even for a lot of the application questions, you can pick up a fair number of marks just with pre-learnt facts, as long as you figure out what the question is asking you about.
There are exceptions, and you do have to manage not to be thrown because they've asked you about an egg rather than a potato, or an axolotl, not a fish- but it is possible to get a 9 basically just through memorisation.
For the A-level I teach, there is a lot more application in unfamiliar contexts, a lot more interpretation of data, a lot more evaluation including, again, unfamiliar contexts. The questions can also be harder to interpret, and the mark schemes narrower. You have to be able to draw links and comparisons as well. We actually really like students to have a good English language grade, as it helps with this!
A small proportion of students, who may still be working really hard, can't make that leap, or struggle with it at first and get disheartened. Therefore, it doesn't always follow a 9 at GCSE leads to a A* at A-level.