I'd be inclined to agree with you. However, the initial implication is that communist leaders are different from random-ass rich people. That means the burden of proof lies on the person saying that.
I said "I'm pretty sure", clearly denoting that this is an educated guess. I didn't say "I know" or "it is fact". This is because I know that finding exact numbers will be very hard, given that I don't speak Korean and don't think that this information is public in any case.
I'd actually be happy to be proven wrong! If you find any good sources, let me know.