Of course it's not incorrect to use Kyoto as an attributive noun. "Kyoto accent" is perfectly correct. The "rules" laid out in that link are more like common patterns, not prescriptions.
Hard lines rarely happen in the real world. It's best to be flexible such that you can accept unfamiliar instances of familiar patterns without trouble.
I'm certainly disagreeing with the part that claims there is an explicit list of correct uses. English isn't that simple. They were cited as a big list of examples, not as having all the rules.
Hard lines rarely happen in the real world. It's best to be flexible such that you can accept unfamiliar instances of familiar patterns without trouble.