Can have assets of a specific type in a site without having the asset type enabled for that site?

In a reset, untouched JSK with the avisports site, you have attribute editors visible under the dev tree tab. However, if you go look in Admin under Sites -> avisports -> Asset Types Attribute Editor isn't one of the enabled types (and there's no 'Attribute Editor' in the New or Search screens either).

You can have assets in a site for an asset type that isn't enabled for that site? How are these created? What does enabling an asset type for a site actually do if it doesn't control what asset types can exist in the site? Is this just something weird/wrong with the avisports example?