Yeah I feel like the results could be stated more clearly. At any rate this doesn't seem to associate risk with any chosen behavior.

This was how I read it as well. Having a neurological issue that causes you to fall asleep in the middle of the day would logically be a good thing to check for correlation with dementia risk. Separate from not needing to nap, but choosing to.

It seems to me that perhaps the data better supports that dementia is correlated with unintentional and short naps. This makes it sound like they think it is causal, which I doubt.

Easily. I'm 80% sure that they did reverse cause and effect.

Yes, ironically they even admit possible reverse causal effect along with many other causal variables. Frankly, this is not exactly stellar research in my view, at least with the rather reckless insinuations not supported.