How are they going to know where you are really going
Yes they will tell from the ticket you have your initial destination, but who is to say that won't just be a stagi9ng post. Any protection they hope to get from this will just be false security that will create another load of civil service admin non-jobs, rely on another overexpensive doesn't work properly computer system and no doubt create even bigger queues at passport control
Maybe this is just a means by which they could consider implementing flight rationing, something that I heard suggested a while ago under "green policies".