Jobson also had diabetes, which tends to result in "mercurial" behavior.
In one of my copies of Hunting Horizons, the 5th edition published in 1993, Sitton was listed as "Executive Editor," underneath Scovill as "Editor." This pretty much means that Gary was hired due to Scovill being over-worked at the time, when the company was rapidly growing.
My one experience with Gary as an editor was when, as mentioned in a previous post, bought my first article for Petersen's Hunting. But as also mentioned by somebody in the link I posted, he wasn't very responsive as an editor: "As an editor he was the worst procrastinator I ever knew, but as a writer he was the greatest talent this business has ever seen. He would almost never write his editorial until the absolute-last minute. Then, after a martini-fortified lunch, he'd lock himself in his office for a couple of hours and come out with something consistently brilliant."
I'd sent Sitton what's known as "query letter," proposing an article. When I didn't get a response within six weeks, I wrote him again--which is what my major mentor in the business, Norm Strung, suggested. (Norm was a very successful writer, both with magazines and books.)
As I recall, Gary's response was that his first obligation was to take care of the staff writers--though he did eventually assign me the article. This was back when probably 3/4 of the content of most hunting/shooting magazines was supplied by freelancers, rather than staffers--which is the opposite of today. In fact some magazines only use staff writers, which does reduce the editor's work-load.
So my guess is that Gary didn't really lean into editing Hunting Horizons as much as Scovill (and Mark Harris) desired.
