I imported a backed up Virtualmin virtual server for a domain that I had never hosted before. The import went fine, but then I just now noticed that under "Enabled features" for this particular server was the option "Log file rotation enabled?" and it was unchecked. I checked it, saved the settings, and then went back to look at my other virtual servers to see if I had missed enabling it for them. Well, the option didn't exist on any of them! It just wasn't there!
So, I went back to check to see if it was still there on the virtual server I just turned it on for and it wasn't there anymore either! It just flat disappeared completely from the "Enabled Features" list.
I guess once it is enabled you can't disable it?