because liquids cannot be compressed.

whomever told you this was mistaken. liquids can be incredibly difficult to compress and may not compress much, but they can be compressed.

Cats move between 3 states of matter at will. Solid when you need to move them from your chair, liquid when you need to pick them up, gaseous when they take up all available space in the apartment. Also occasionally plasma, if they’re sunbathing for too long

In the game “cats are liquid: a better place”, the cat you play as can turn into a gaseous form, which can be compressed

That happening in a game called “cats are liquid” means that cats can be liquid and compressed at the same time