As far as I suspect, many of the White Nexus 4 had Android 4.3 installed and hence Google intercepted them.
"It looks like Google is calling this one a case of incorrectly assigned tracking numbers. The good news is that your new white Nexus 4 should still be on its way, and Google will be updating any affected shoppers with correct tracking info."
"A small number of customers were sent a ship confirmation with an
incorrect tracking number on 5/31 and 6/3. In these cases the incorrect
tracking number may indicate that the package is being returned to
Please disregard this tracking number. Another ship
confirmation with the correct tracking number will be emailed to you
within 24 hrs. Please reference the tracking number in the 'Thank You'
section of the ship confirmation.
Please rest assured that your package’s arrival date is unaffected by the incorrect tracking number."