Thanks for the insight. That sounds like what I'm finding as well. When I was younger, it wasn't seen often. After some tendonitis in the shoulder it seems to rifle/spiral at times. Like you, I'm about 6'3" and long arms. My no spin is also mostly inside the 10' marker. Even on the high speed camera at 240 fps I can't catch where it's happening, but I feel like you're correct. If I used stinger type knives maybe it would be different, but since I was originally trained for tactical, not competition, I don't throw anything I wouldn't carry. As a friends of mine likes to say, if you wouldn't carry it to kill a zombie, don't bother using it for throwing practice. :>)
Thanks again, gentlemen.