I believe that note is in contrast to Scala 3’s 0-based integer indexing. For example:
scala> val t = ("Hello", 42, true)
val t: (String, Int, Boolean) = (Hello,42,true)
scala> t(0)
val res0: String = Hello
scala> t(1)
val res1: Int = 42
scala> t(2)
val res2: Boolean = true
scala> t(3)
-- Error: ----------------------------------------------------------------------
1 |t(3)
| ^
| Match type reduction failed since selector EmptyTuple.type
| matches none of the cases
|
| case x *: xs => (0 : Int) match {
| case (0 : Int) => x
| case scala.compiletime.ops.int.S[n1] => scala.Tuple.Elem[xs, n1]
| }
1 error found