It's not about the math at all, just "this seems like the wrong group to use as an example". It's a simple point, nobody is trying to show off.
And in these comments I'm assuming that the author has exactly the right number for the group they cited. Because it's really not about math. I have done no calculations and trust the number given. I just think they're citing the wrong statistic. That's why I'm also uninterested in the factors you mentioned that might influence the number up or down. The actual number doesn't matter for this criticism: even if the number in the article happens to match the right statistic, they're still citing the wrong statistic.
And in these comments I'm assuming that the author has exactly the right number for the group they cited. Because it's really not about math. I have done no calculations and trust the number given. I just think they're citing the wrong statistic. That's why I'm also uninterested in the factors you mentioned that might influence the number up or down. The actual number doesn't matter for this criticism: even if the number in the article happens to match the right statistic, they're still citing the wrong statistic.