Stelle units in Bulge 44

[Green]

I believe you are referring to the Brian Jennings Herbstenebel scenario. This is just of the top of my head as I don't have time to check and have the Gold version of Herb as well as the original so I tend to get them mixed up.
These units are artillery spotters.
Definetely not deception units.
In the Gold version, I believe some are single use simulating the German bombardment, then they and their artillery  units are removed to arrive later as reinforcements.
There is a read me file.

Yes, they are only relevant to the Herbstnebel campaign. The Notes say;

"Most German Nebelwerfer and Volks-Artillery-Korps units initially on the map are single use and will be removed at the end of the German first turn. Use them before you lose them!! They will then reappear as fixed reinforcements and will be released over the course of the next few days."