Equivalent to a 90mph Fastball…. huh?

Football announcer: Brett Favre has got a cannon of an arm, that last ball he threw was 46mph, equivalent to a 90mph baseball fastball.

What the hell does that mean!? Where do these guys came up with this stuff!? How is a football pass equivalent to a baseball fastball? Wouldn’t a 46mph football be equivalent to a 46mph baseball, they’re traveling at the same speed.

Can some one can explain to me the bizarre world of sports announcer physics?