I don't know where you live, but at least here (Italy) locks that have "contractors keys" can only be opened with contractors key until the "proprietor" key is

I don't know where you live, but at least here (Italy) locks that have "contractors keys" can only be opened with contractors key until the "proprietor" key is used once (with an "installing maneuvre"), and then contractors key won't work anymore. What you describe is more like the master key systems (used as an example in some hotels) where there is generally a three level (but there can be more) set of keys, the manager's one (that opens all doors/locks), the maid one (that opens - say - all doors/locks in a floor) and the actual customer one where each key only opens a single lock.