Richard,
You are most probably correct; contour
"fighting" is probably a progression from the term contour
"flying". The term "contour flying" is seen often in the literature of the period, by coincidence I''m presently reading Yeate's "Winged Victory' and he uses the term a lot.
The discipline of Ground Attack Flying and Close Air Support is a very dangerous one, it has always been so and in my past experience we flew very low to minimize the threat from ground forces while optimizing the probability of a successful attack on the target(s). This included ingress and egress into and out of the battle area at very low level (200 feet above ground level) at high speed following the contours. Some delivery profiles were at 100 feet above ground. The development of "smart weapon" technology has changed a lot of that today. In 1918 the delivery of weapons onto ground forces was very basic, thus they did their work in close, very low, and with bullets and a lot of hand launched weapons such as the grenades we see in the photos. Brave men those, on both sides of the conflict!
I wonder if the book referenced earlier, "Schlacht-Flieger", might shed further light on the topic? Bottom line though is I gotta get me one of these Halberstadts!

Cheers,
Lance