[w0000t]

That is not what OP is talking about. You cannot get different information out of the same chunk of encrypted data. That would basically make infinite compression.

What the methods you mentioned are doing, is hiding information in places which are marked as: random data no information here. But in reality there is information there. You then need to have dummy information somewhere else.

[grumio]

This would be trivial to do with one-time-pads. A bit bulky, but simple. But in a way, you'd still be right. The "dummy information" is (encoded into) the second key.