I think you are right about SG. As I recall Don wanted mostly NG, but the primary focus was photography, and steam as well as Narrow Gauge. The focus was also on prototype railroading, not modeling, although some was allowable, presumably when about NG railroads.
Heck I have seen threads on aircraft(Some I started), but mostly vintage WW2 historical stuff, various modern subjects like Union Pacific 3985, 844, and Big Boy 4014, historical photos and questions, and even off topics besides trains. I think the best way to handle it is as many posters do...put NNG(Not Narrow Gauge), in part of your thread title. This way if someone doesn't want to watch, fine just skip it. Foreign topics are okay too once in awhile, and witness the photos from Anthony. Good photography is okay by me, even if electrics in Switzerland. I can skip it if I wish. Like John said I too am a steam fan first, and it just happens that I mostly enjoy the ex-D&RGW NG the most of all the NG, except maybe South African Steam, which is SG to them, NG to us. Stray topics can be a good thing for variety sake. Some NG topics are overly covered anyway. This year it looks like fire season and closures might be overcooked, but maybe rightly so. I would rather see some photos or news of new steam running, like 1309, 2102, or others than NG diesels for example. Just my 2 cents, which is worth less than a penny in today's economy.
Greg