<blockquote>I think you're using too many tests for "border-box", "content-box", "available", "min-content", "max-content", "fit-content". Why would a browser implement them for min-width and not for min-height for example? I think it would be sufficient to test four max (perhaps width, height, min-width, max-width or something along these lines)</blockquote>

Because each browser for the degree of realization of min-width and min-height is not the same.