6000PIC
If that is the objective, fine. But I don't see this as meeting that objective. All you do is increase the Immigration people's knowledge of those that followed the rules. It doesn't increase their knowledge of those that do not follow the rules.
Why don't they require sea/chunnel operators to collect APIS? Why don't they ask airlines (and sea/chunnel operators) to advise if/when a non-EU passenger no-shows their return journey? Now that might be effective.
As someone familiar with intra-schengen travel, travelling to/from the UK is already a pain. And this 'verification' is going to make it worse, much worse. Even if it added only 30 seconds to each passenger at the gate that's an hour for 120 passengers.
By all means protect your borders, but please, do it in a way that is effective and doesn't penalise the vast majority of people who are no threat.