As I understand it the main point about the Modern Slavery Act is about the referrals process. The reason they call it a "loophole" is the huge increase in referrals from civil society organisations claiming that illegal arrivals are victims of modern slavery when in fact they are economic migrants.
The Home Office makes a decision on whether a person is a real victim of modern slavery or not, if they decide they are then the person gets full protection during a period of recovery. However, once the person is freed from whatever unfair enslaving agreement they were subject to and also recovered from any injuries they are evaluated against immigration law criteria.
The great majority of the increase in referrals under the Act are people from Albania, Albanian nationals were about a third of all referrals last year. That's why they made the agreement with the Albanian government on take backs. Once an Albanian citizen is free from slavery and healthy it is very unlikely they will get permission to stay in the UK.
You can like this system or not like it, but it has nothing to do with Germany in the 1930s. The fact the UK has a Modern Slavery Act that is enforced is a bit of a clue that there might be a difference.
Ok .. but we're talking language & rhetoric. And boasting online that people 'won't benefit from illegal slavery protections' falls under the kind of langauge being referred to.
Maybe it doesn't .. for you. But it does for me, and others. And seemingly for people who had to go through the worst atrocities in human history.