I'm not sure if this is a change that I'm not aware of or if this is a bug, but I have the ability to place cactus on the main server rising world (might be network wide). As far as I am aware, cactus has always been blocked from being placed/growing because of autofarming it.

Again, if this is a recent change, I was not aware of it, and the people I asked weren't aware of this change (if it was one) either.

Below is a screenshot of cords and a nice cactus farm that I found in the rising wild, which caught my attention.

 

Ah ok. I was inactive a few months ago, and I guess the people I asked didn't know either lol.