I must say I'm not sure about the food regulations regarding the way the grain is being harvested, but you are spot on with the rest of your comments.
We do sometimes have to keep harvesting, when the occasional shower comes by - since we don't have the long hot summers that some people here have, we have to get finished while the weather is still "ok".
I'd say about 90 % of the harvesting done here in Denmark, is done within a 2 week periode... Note that harvesting at night is rarely used here due to moisture going up at sundown
Nothing to do with food safety at all. They are simply like that so they fold neatly within width and height regulation for transport on the road. The latest Claas 600 actually has extensions that look like the American type BUT they fold shut with linear electric motors and seal the tank shut. It is possible to harvest with the lids shut on all of the Lexion combines from Claas but only for a short while.