tanaguru color contrast for accessibility

The following 3 URL's give 3 different results from the tanaguru page ... and are all accepted by the tanaguru Firefox plugin.

http://contrast-finder.tanaguru.com/result.html?foreground=%23AA3333&background=%23330000&isBackgroundTested=false&ratio=4.5&algo=HSV

http://contrast-finder.tanaguru.com/result.html?foreground=%233333AA&background=%23330000&isBackgroundTested=false&ratio=4.5&algo=HSV

http://contrast-finder.tanaguru.com/result.html?foreground=%23006600&background=%23330000&isBackgroundTested=false&ratio=4.5&algo=HSV

In each case the background is the brown of #330000.

All of the results are acceptable contrasting colours for text on a brown background ... but I think what a better tool might give is a carousel of results.

Am I missing something ?

Here are my setting :

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