It's much simpler than that: honest mistakes get marked as fraud, and immigrants are much more likely to make such mistakes due to the complexity of these systems, especially when 'assisted' by entrenched operators trying to make a quick buck whilst escaping liability. As a Dutch native speaker I've been more than once utterly flummoxed by the way certain official forms are worded. A non-native speaker doesn't stand a chance. And then of course you get the book thrown at you while meanwhile your average fat cat commits tax fraud with impunity because they can drag out the case and afford themselves the best lawyers if they are ever investigated, which rarely happens. These cases are so rare they actually make the news. But oooh if you are a contractors and you drive 50 km too much in your work van, then you're really in trouble.