I once had a seller insist she lived in the UK even after I pointed out that the system told me her timezone, which was the same as Pakistan. The thing which made me suspicious in the first place was that she didn't know the blue area on a map is the ocean, which seems a very strange thing for anyone from the island of Great Britain not to know.
After having hired probably about 15 illustrators for different children's books on Fiverr, I've come to screen them very carefully. Firstly, I eliminate anyone from either Nigeria or Pakistan (though I have hired a Bangladeshi twice). Then I filter by price and look for the style I'm after. As the format of my books creates its own challenges, I then spend a while chatting with them to check whether they're up for it or not. Some politely pass, which I honestly prefer to those who say they can do the job but lack the skill.