You land on the runway...that's the rule isn't it? If its not part of a runway, don't try and land on it.
I'm sure a few of us may have touched down a smidgeon before displaced thresholds on occasion, but then a few of us may equally have been guilty of the odd tiny CAS or land clear rule infraction, these are equally valid rules which we should aim to stick to.
Not saying I'm perfect mind, far from it!