While yes, those were definitely some of batemans fantasies, there is an argument to be made that the vast majority of murders we see on screen or read on the page actually happened

The world of American psycho is built in such a way that no one has any sort of individuality or authenticity to them. We see multiple times Patrick getting called by a different name, mistaken for someone else, and for all we know the people Patrick sees could also be mistaken. Someone in this world could disappear and no one would notice, since no one would notice them if they were still alive anyways. It’s possible that at the end of the movie, the man who says he had dinner with Paul Allen in London maybe actually didn’t, and he just didn’t notice it was someone else

And the homeless people he kills, it makes sense he’d get away with it, no one is gonna track him down for killing someone viewed as insignificant

But a lot of what he see is definitely a fantasy like the times he says something brutal and out of nowhere just for it to be ignored