Hi Peter
Orion is visible in the night sky from September, given that the weather was a little more clement in the Neolithic and Bronze ages, this means that their first sightings of Orion could be on warm balmy nights much as happened this year.
So rather than a winter marker, Orion may have signified the end of the agricultural year and the beginning of the hunting season. Perhaps the German Rake and Mower weren't too wide of the mark also perhaps Orions portrayal as a hunter also fits the bill too.