What is the radius of a circle that has a circumference of 1 (as proposed in TFA)? It is 0.5/PI == ~0.15915, which means you are just moving the "problem" elsewhere. I am sure there's a lot of math that is simpler with radius being 1.0 (with some input in radians) vs an input in "turns" and having to deal with a 0.15915 radius.

Yes, agree turns would be so much nicer for many use cases, but I'd like to see which operations it makes worse first :)

If indeed almost every hardware/library implementation of `sin` would lose a multiply by an arbitrary constant by choosing a new input scale, that would convince me too, as long as it was the same scale for all.