There is a fundamental difference between modelling dioramas and the type of setup/take down "scenes" you see displayed here.
A modelling diorama is permanent so everything can be geared towards a single scene. The positions of the figures may be very specific, the suspension of an AFV may be adjusted to fit the terrain, Water features can be involved (i.e. vehicles can be partially submerged). the terrain (i.e. tracks, disturbed grass etc.) can be set to correctly match the action in the scene, weathering can be done to properly match the conditions (i.e. muddy, dusty). The fun of these scenes is getting every detail right.
The setup/take down type scenes we mostly see here are what is possible with off the shelf figures and vehicles. Many compromises have to be made starting with something as simple as the figure base. The fun of these type of setups, at least for me, is the reusability which facilitates creativity. It's a lot of fun to take a number of modular components and to arrange and rearrange them into a wide variety of scenes and stories. Are they ever going to look like Dr. Shige's (Shigeyuki Mizuno) work? of course not, but that sort of detail would be cost prohibitive for non modellers like me.
