But it’s not theft, because you’re not redistributing. It’s allowed, just like humans are allowed to learn from copyrighted content.
You don't need to redistribute the original material, it's enough that you just copied it.
This is what should be fixed in the first place, then. You shouldn't get sued from what you do with your copy of a song.
humans learning : machines learning == whale swimming : submarine swimming
It's not the exact 100% same thing. Therefore you cannot base any rights on it.
If you still don't buy it, consider this analogy:
killing a human vs. destroying a machine
Thank god that we're not using your line of thinking here.