This happened previously too, South Korean LG manufactured Google's 2012 flagship Nexus 4 was also a part of this treatment. And now we have the company's latest model too undergoing minor hardware tweaks with their latest shipment.
Junior XDA-Developers forum member made in note that, due to several manufacturing defects, many of the users have chosen to send back their devices to receive a new one in it's place. The defects were basically described as, "Dancers and Noisy Buttons", "SIM card tray protruding" and "Cutting edge display frame".
As the reports suggests, the new products are hitting the store shelves with better and larger speaker and microphone holes on the bottom and the buttons seems to be more firmly fixed. But according to the newly built screen, the new models come with a more yellowish display and a few green struck pixels. So if any of you have the new updated Google flagship, do let us know, how you feel.
Source: XDA-Developers