MDC, including Quinton, reads the forum. Let them answer for themselves.
Personally, I don't think there's a clear answer. If Quinton, or any other agent, thinks a fly is illegal and can convince a judge that he's right (good luck!), then it is.
Gummy flies are obviously soft plastic. There are other materials that are more borderline. It may go to intent, too.
The main reason soft plastics are illegal in trout management areas is the fact that soft plastics can be impregnated with scent. But any scented fly is illegal too.
If you get ticketed with a questionable fly and it's obvious that it was an honest mistake or it's a borderline case, take it to court cause I almost guarantee the judge will cite in your favor. Heck I've seen a judge rule that even he has trouble distinguishing between a rainbow and brown, how can other fellow fisherpersons!