I have a pretty good idea of why it's doing that. On the "X330," the display is technically an external display. My understanding is the connector is soldered to one of the docking station port's DisplayPort lane. The internal LVDS connector is disabled by 1vyrain.
I had the same problem in Mint but there, I was able to solve it because it included an option in power settings to suspend when connected to an external monitor. It's an option in Elementary OS as well but I decided against using it because I didn't want to take the time to get used to the more MacOS-like UI.
So far, the only solutions I've been able to find seem to be for the opposite of what I'm trying to do. Does anybody have a solution to this? Thank you.
EDIT: For anybody asking why I left Mint, it's because for some reason, I could not get the TrackPoint sensitivity to work properly on that distro. It works fine in Mint on my T410, T430, and T15g but not the X330.