Right. They justify this by radiation and impacts, but without giving any numbers. Those were certainly considered back in the 70s. https://en.wikipedia.org/wiki/O%27Neill_cylinder#Atmosphere_...

This video might be interesting for you: https://www.youtube.com/watch?v=gTDlSORhI-k

Aren’t O’Neill cylinders with liquids inside inherently unstable?

If memory serves you have to spin them along another axis or they will wobble and then flip.