I don't think so. I think what is happening is that most people are not familiar with hippos because probably somewhere between zero and one people in this thread have ever seen them in their natural habitat. The average person might think hippos swim because they do not understand that hippos do not float. If you were to put a hippo in a very deep pool they would simply drown, because they cannot float nor swim. I think if you clarified this, most people would not continue to assert that they are swimming.
Specifically I found these citations very helpful:
https://news.ycombinator.com/item?id=36777376
So I think what we can say is that the average person would be wrong about hippos, because the hippo is not actually swimming but people do not realize that. We expect LLMs to behave more like an expert, so the standard is even higher and we should be more willing to say it is wrong.
Although the meaning of a word is defined by its usage, there are also common misconceptions that people have. It is not the case that every usage of a word is correct. Instead you would have to ask a variety of people what swimming is, and then describe to them what a hippo does (it does not float, it walks on the river bed), and then consider whether that fits with their conception of swimming.
I think what is happening here is that lots of people thought hippos swim, they have been corrected, and now they are feeling a bit defensive and trying to save face rather than say "huh that is interesting I did not know that hippos don't swim".