Well, to me that sounds a bit silly. The only real difference between an .mpd and a .ldr is the file extension. I mean, you can name a .mpd a .ldr and it would work fine in most software.
If the model is small or simple enough that it doesn't need any submodels, an .ldr is enough right?
If the model is small or simple enough that it doesn't need any submodels, an .ldr is enough right?