Sony Mobile Singapore today provided an update on the gap issues that we reported in April.
According to Sony Mobile Singapore, it has not received any complaints about the Xperia Z2's or even the Z1's waterproof capabilities being compromised by the "perceived gap issue". It recommends users who are still concerned to visit the Sony service centers where the staff will help conduct a water resistance test.
HardwareZone had handled three different units of the Xperia Z2 (black) in the past month and found no gap issue on the devices. Since the perception of the "gap" is subjective and there hasn't been a case of the waterproof feature being compromised, it's unlikely to be a concern among Xperia Z2 users. If in doubt, you can always visit the service center to clarify and get your phone tested.