I'm not surprised.
But most people are surprised by the possibility that we have three eyes, where the third eye is a good illustration of how evolution can happen.
The significance is solely - but importantly - in the context of those that claim "full eyes couldn't have evolved from fractional eyes, because only full eyes are useful; therefore evolution couldn't have produced us".
It destroys one typical argument used by those that don't believe we could have been implemented by a "*Blind* Watchmaker".