Although we could recommend an extension to the 0 !LDRAW_ORG statement to identify model files (e.g. '0 !LDRAW_ORG Model'), enforcing that in (text) files not managed through a 'system' would be impossible. All files in the official LDraw library do have a valid !LDRAW_ORG statement.
All parts do have a 'category'. If no !CATEGORY statement is present, the first word of the description must be in the category list. This is enforced by the Parts Update process.
All parts do have a 'category'. If no !CATEGORY statement is present, the first word of the description must be in the category list. This is enforced by the Parts Update process.
Chris (LDraw Parts Library Admin)