Screen tearing with video on laptop monitor but not on HDMI with external monitor. Why?

I have an Acer c720 chromebook which I believe uses intel HD 2000 graphics and have noticed that tearing on video goes away when I use an external monitor through the HDMI out on the laptop. I can use the "tear free" option to get rid of tearing on the laptop's monitor but with HDMI it happens automatically? Why would this happen? Is it using a different method to v-sync? I would prefer not having to set the "tear free" option because of potential issues with other programs.

At the moment I'm using Fedora 20 with the latest downloadable drivers but it happens on every distribution on every version of the intel driver I've used.