The details are unclear anyway. What about Schengen citizens living in the UK? I can imagine they'll generally let people in from UK and Ireland but question them about travel history and maybe proof of residence. Lying to a border agent gets you banned for life, that should be a decent deterrent.

In the end, it's not like a terrorism threat where the ones trying hardest are the ones you need to catch. Here, keeping 99% out can suffice easily, esp if the others are also questioned and are getting temperature checks.