We have a category for real that differentiates from drawn. We have a category for furry that differentiates from drawn. All furry is drawn/3d, but not all drawn/3d is furry. Primarily because people don't want to see it, or at least don't want to have to hide the threads they don't like or don't want to see, and would like to see it sequestered into it's own little corner. Or because the categories are just 'neater' in their own little wings of the site, where no one who doesn't want to see them, has to see them.
There's virtually no logically consistent argument you can make that should make it feasible for furry and drawn to be separated that should not also apply to mpreg art and photomanipulation :). So I propose either re-integrating drawn and furry, or giving mpreg it's own category. As it is, the differentiation is flippant and seems to matter more on what certain people like vs. how much content something has.