I like the idea of freezing shampoo because it is rather silly, and illustrates the silliness of the whole rule. I am also quite sure its not something seen at the checkpoint every day. I have done a "test freeze" and it does get totally solid, and lasts quite some time without thawing.
We'll see how it goes. I have quite a few connections and trips on different days, so I can test quite a few frozen goods.