When I was a kid, the range was 1 mile. I assume lawyers got involved at some point and increased the range.
They said one mile when I was a kid too. They have said 1 and a quarter mile for some time.
I read a controlled test a few years ago and the farthest they could get a .22LR high speed was around 7/8 of a mile. I guess they have to cover every possibility in their warnings. Maybe a hundred mph wind blowing the same way you shoot etc.