Aaronw is probably correct. Kalmbach may segregate subjects according to their publications.
I have been modeling everything since the 1960's and see no distinction myself. In fact, what I know about weathering and dioramas I learned from modeling railroads! Current projects, now that I again have time are:
1) Picked up a Model Shipways Gjoa I started 25 years ago. I have posted a progress shot of this in the "ships" section here. Getting my "sea legs" back with this model before attempting the much larger and demanding No. 2 on this list.
2) Found a 1/8" scale Model Shipways Frigate Essex and it goes up next
3) Africa diorama involving Tamiya's 1:35th scale Stuart in British Desert Rat drag, Tamiya's Brit 8th Army figures, and MiniArt's 1:35 Brit Tank Crew
4) Bowser USRA Mountain locomotive in HO scale, super-detailed for the Central of Georgia according to prototype photos
5) Korean War air combat diorama involving Minicraft's North American F-86F Sabre and Airfix's MIG 15, in 1:72 scale
6) Revell's Robert E. Lee paddleboat in some diorama situation not planned yet
7) HO scale train layout representing typical Southern US railroading, with Southern Railways, Central of Georgia, and Georgia Railroad equipment running on interchange tracks
8) If son does not remove from our basement soon: Russian Winter diorama involving T-3x ? (too lazy to go look) tank, German and Russian figures, etc.
9) Graf Zeppelin - in fact, leaving today to visit daughter who found it at a discount store and bought it for me...
So anyway... happy to see all the great stuff you have here: I hope to learn much by studying your posts... just include a locomotive or train every once in a while...