In high stick nymphing, you are still using a fly. Not a jig. And you stated it perfectly. A fly is tied. A jig is molded. I have fished micro jigs on my fly rod, just as I also use live bait with my fly rod sometimes. It works, but it doesn't 'feel' like fly fishing. It feels like I am using my fly rod as a spinning rod of sorts (and I do use a spinning reel on my fly rod sometimes.....), just the opposite of when I have used a casting bubble or float to cast flies with my spinning rod. It works, but neither of these 'feels' like fly fishing. I am not saying I am right and everybody else is wrong. It's just a personal thing. And as far as I am concerned, anything that is legal, and puts fish in the basket is OK by me. It's just that traditional fly fishing has a 'feel' to it that is almost spiritual, sort of like doing Tai Chi in the water. When I use other things besides flies, that feeling just isn't there, for me. It's just catching fish (which is also OK).
Fly fishing means a lot more to me than just catching fish, and it is very important to me.....as I said, almost spiritual. It has allowed me to function in a world that I often feel ill-equipped to live and work in. When I fly fish, I feel like I belong, even if just for a little while. So if am a little over-protective of it, well.... I come by it honestly. And I mean no harm to anyone, ever. To each, his own, with my heartfelt blessings.
Maybe I am just weird. It wouldn't be the first time I have been a square peg in a round hole.