I have noticed it also on my drivers side rear lights.
If one side does it and the other does not clearly there is an issue that years down the line will cause an issue.
A combination of the clear lights, condensation, not a sealed unit and LEDs not creating much heat causes this and it is not going away with a replacement of another 'not sealed' unit.
It doesn't look good but doesn't really affect the functionality of the lights so that they don't work, I'm not saying its right but they are only going to replace the unit with another unit that will more than likely have the same issue.