Let me use the analogy of a bank for a minute...

I need to keep my secret cookie recipe safe. When I take it down to the local bank, they offer to put it inside a locked box with only one key and then put the box in their vault.

If law enforcement shows up with a warrant, the bank is legally obligated to open the vault and hand over the locked box.

Now here comes the curve ball... IF the bank kept an extra key to the lockbox, they can be compelled by law enforcement to open the box. Otherwise, it is the law enforcement agencies responsibility to either get a locksmith to open the box, or force me to provide the key.

Dropbox is the bank that keeps an extra key, even though it creates legal liability. Furthermore, they lied to you about keeping the extra key when you first stored your cookie recipe.

So that sentence I quoted is basically a lie.

It wasn't a sentence, it was a qualified clause: "To be clear, aside from the rare exceptions we identify in our Privacy Policy, no matter how the Services change, we won’t share your content with others, including law enforcement, for any purpose unless you direct us to."

Oh, duh, I don't know how I missed that part :/