As an update to this, I did a little trial and error on this.
If you intentionally leave the gate open, and the dinosaurs are roaming generally without any bars in the red, they will not run out of the gate but look at it. I have yet to see a stable dino run out of the gate.
If the dinosaur is panicking, there's an extremely high chance of it escaping through the gate.
If the gate is left open for the meat-loving dinosaurs, there's a decent chance they will run out just because FREEDOM! Seen this twice with Velo's and Dilo's.