> If the rule is meant to allow expats to still participating in voting in their hometown

Is the rule meant to do that? I don't perceive that to be the case. What even is a hometown? What if someone doesn't have a hometown? What if you leave and never plan to return?

Decidedly expats do have real business in voting in elections otherwise this rule would have been removed. But it would be unconstitutional to tax citizens abroad upon depriving them the right to representation so this seems. Given there seems to be no appetite to disowning American expats this all seems moot.

I'm not aware of any other country with this sort of policy. It certainly seems to me that you get precisely what you ask for here, and there is no possiblity of abuse.