The first section explained what kind of VPS were collected. Vultr sometimes charge estimated monthly costs (https://news.ycombinator.com/item?id=13073048 ) , so it was not listed.
I've been using Vultr for years and they've never charged me more than my monthly usage. A n=1 report from two years ago doesn't seem like a great reason to leave them out; I'm sure you can find complaints about every other provider's billing as well.
I was charged that way in March this year. Then I googled and found that they do such thing often.