[stouset]

Yes, of course it leaks more information than encryption without compression, because that’s just encryption which doesn’t leak anything.

In an enormous number of real world cases adversaries can end up including attacker-controller input alongside secret data. In that case you can guess at secret data and if you guess correctly, you get smaller compressed output. But even without that, imagine the worst case: a 1TB file that compresses to a handful of bytes. Pretty clearly the overwhelming majority of the text is just duplicate bytes. That’s information which is leaked.