Depends what types of questions you're doing.
End of chapter problems are usually content review, so being able to do them very well demonstrates a closing of the knowledge gap. That's good, because while the MCAT is certainly a 'thinking' exam, you do need to know a lot of content to be able to apply it. But keep in mind that the MCAT is almost all passages, so you'll be given passages about things you've often never heard of, and then you have to relate it back to certain topics, or realize that they are talking about something that you know, but presenting it in a different context.
Therefore, having a solid knowledge base is crucial; but keep in mind, that if you aren't able to draw conclusions, parallels, digest what's important in a passage, simplify the problems, and do this all quickly and somewhat accurately, then you'll have a bad day. Plenty of people "know" the bare bones, rote memorization formulas, concepts, and key facts. But you have to meet the MCAT halfway (hell, all the way), and apply it in new situations.
So to answer your question: not necessarily.
If your practice questions correspond to a passage, and you can do them timed, then obviously that's a good thing. But nobody knows how you'll do on the MCAT. Of course it's good to know things. That doesn't mean you'll be a rockstar at it during an exam when shown information in a new context.
