They are not sealed by design. I dont know if there is a single car with sealed headlights sold in the USA anymore. I think those went extinct in the 90s. Unless BMW has updated the design and airflow/ventilation, you should be getting a light with the exact same poor ventilation as the original
Most manufacturers will supersede the part number when a meaningful revision is made to a part, so that could possibly help identify if you are actually getting one that wouldn't do the same thing given the same sequence of conditions.