Sorry, I wasn't clear. Let's try again. NFHS rule set. How long ago was it that excessive spin could result in an illegal throw-in?
Not so. While I can't tell you when the interpretation changed, in the 70's, there absolutely was an interpretation was the "use both hands" language of then Law XV implied that something akin to equal force of the hands needed to be used, and that meant that the ball could not be thrown with one hand and directed with the other. Per that interpretation, significant sideways spin was considered an infraction, as it indicated the ball was really being thrown predominantly with one hand. There was, of course, no ATR or I&G back then, and the issue was not addressed in the the then Decisions of the International Board from IFAB. The most authoritative secondary source I knew back then was Fair or Foul -- one of the authors was an NASL [that's the old NASL...] referee, as well as AYSO's director of officiating. On this issue, Fair or Foul did not distinguish amongst HS, college, and FIFA. The fact that it was once the actual interpretation is perhaps why it is such a persistent myth (under modern Law 15), especially amongst those who played back then (i.e. dads coaching their kids....).
I remember that from when I was little in school. I tried to spin it once and a teammate that played Select told me that wasn't allowed.
Copy right date on my Fair or Foul is 1975. My recollection (somewhat vague after that many years) is that overtime enforcement of that interpretation softened so that only really obvious calls were made (trifling, I suspect was the thought process), and eventually the interpretation went completely away. (Can't tell you when, as I was away from reffing for about 20 years.)