[Citation needed]

I don't think any country invites and then carries out a massive purge of existing labor as it sees fit.

If it does, then it won't be appealing to the class of person you're seeking to attract.

> [Citation needed]

Perhaps you could attempt to steel-man why point-based immigration allocate and de-allocate points for certain professions over time? Or why temporary visas exist in the first place.

> If it does, then it won't be appealing to the class of person you're seeking to attract.

Such is the nature, complexity and self-contradicting character of any large-scale public policy; and it's "classes" (plural) because immigration cuts across social strata, not just your software and service industry "rockstar" geeks.