Maxing out your credit is a red flag that lowers your score. A sudden increase in usage is also a red flag, as people tend to use up all their credit before defaulting.
If you want to charge 20k you should have 60k or more credit. Think of like tow ratings: you don't really want to use it all.
Never fucking mind that I paid the damn thing off completely 2 weeks later - complete and utter bullshit. But you're right, that's exactly how it works, as nonsensical as it is. I wouldn't care except it also affects my insurance, something I didn't know going in. "Highly Accurate" my hairy ass.
So I guess I gotta keep on getting more credit that I don't need so I can use the credit that I do need when I need it. Or get $100K, max it out and skip to Rio. My bullshit meter is pegged...