A couple of thoughts:
First, that Hoosier wet tire IS a DOT tire.
Ya' see, some sanctioning bodies require certain classes to run street tires (with the thought that that will limit the amount of "cheating" done by tire manufacturers. Silly sanctioning bodies!)
Second, racing tires - even wet weather racing tires - have a heat problem - and that limits what tread compounds can be used. They can't use regular street compounds. Those run too hot at racing speeds.
Third, NHTSA (DOT) only requires that the UTQG rating not to over state the ability of the tire. They don't have to test then so long as they don't EXCEED the rating. So a 40 C A is such a low rating that almost any tire will pass that rating.
The fact that all Hoosier's tires offered thru Tire Rack have a 40 C A UTQG rating does NOT meaning they have the same tread compounds. It only means that Hoosier assigns those extremely low values in order to meets the Government regulations.