The Slovakian guy didn't clue them in that he was speaking a real language.
He gave the hospital cover to pretend they didn't know the whole time. Cover to pretend it wasn't just cruelty for its own sake, perpetrated by bigots decades ago and continued by hospital administrators and staff who knew that if they didn't look the other way, they'd lose their jobs. Sure, probably nobody there knew Hungarian, but they've heard of other fucking languages. Jesus people are the worst.