He even showed me a Technicla Bulletin from Skoda France explaining ot was normal.
Indeed, as I mentioned above, it is considered normal up to a certain degree... If you search for pictures, you'll find cases where the headlight is completely covered on the inside, not by a layer of mist, but water droplets. That raises a security issue, since the light will be reflected all over the place - there'll be less visibility and oncoming traffic will be dazzled.
At least Skoda (maybe others too) was replacing some headlights under warranty on Octavia mk4 - there are quite a few pictures on the Octavia forum (UK). Also, the dealership plays an important role in this process... some will just send you away invoking the Tech.bulletin you mentioned), others will pay more attention to each particular case.