Am I missing, like, a lot of context that would make this make sense?

My first thought was like Harbaugh's -- all else being equal, an incompletion obviously gives us better field position than an interception.  As someone pointed out, however, crazy things can happen when attempting to bat down a ball, and Lewis was outstretched.  If he batted it into his leg, it could have taken a crazy bounce, etc.  Roundtree's 2012 catch against Northwestern is the example I think someone mentioned; doubtless there are others that are even more on-point (ball hits defender's foot/leg, bounces up, etc.). 

Regardless, Lewis did seem to float like MJ launching from the free throw line.  It is a beautiful thing.