Combining an avocado and a chair into one image is evidence a model conceptually understands both, not that it memorised pictures of them.

when you can basically bridge the concept of an avocado and a chair and show that you kind of can combine those two, it means that the model has at least some kind of conceptual understanding of what an avocado is and what a chair is to the point that it can combine them into something that exhibits both concepts at the same time.