Yes, apt caches stuff. I'm not actually sure what benefit it has and why it does so. I don't think you can turn off the behavior - but you can clean up after it. You have a couple of options to do so easily. Well, you have a zillion options - but I only go through a couple.
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How To: Clear The apt Cache • Linux Tips
In today's article, we're going to learn how to clear the apt cache. This is only useful if your distro uses the apt package manager.
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Feedback just is alright by me.