SLR lenses are kind of similar. They can have scratches and chips that don't impact image quality. Has something to do with optics and focal lengths. But yes, it can catch lens flare.
I just can't figure out how mine cracked as it's never been dropped or impacted. I guess the hump can put some strain on that spot.
SLR lenses are not as much affected by scratches since they're larger in diameter; i.e. the relative size of the scratch compared to the aperture is a bit negligible. But, in all cases, scratches and smudges will produce lens flare from incident light sources.
But back to your issue, I'm not familiar with the material surrounding the lens cover in the L1520. If it's plastic (polycarbonate), then occasional warping due to the large footprint of the phone could have caused the cracks. But if it's aluminum (just like in the L1020), only strong direct impact and pressure can crack it... unless it's a factory defect.