Cooling off period for Tier 2 General

[ShrutiBlue]

According to this page and also the Tier 2 Policy Guidance, if a Tier 2 migrant leaves the UK, they have to serve a 12-month cooling off period before they can re-enter as a fresh Tier 2 migrant.

What I don't understand is, does this "leaving the UK" mean leaving after quitting your job/having your employment curtailed or when your current Tier 2 expires? Are holidays while you're still on your Tier 2 and still working for the same employer included (I'm guessing not, but still want to confirm)? The language on these documents makes it sound like a Tier 2 migrant is bound in the UK!

Thanks!