In Silman's Complete Endgame Course, the author gives this rule in order to gain the Opposition when there isn't a direct connection in between the kings:
In this type of situation, the rule is to make a square or rectangle in which each color is the same color with the other guy to move.
But later in the book, this practice problem is given which seems to contradict this:
[FEN "2k5/8/8/8/1PK5/8/8/8 b - - 0 1"] 1...Kb8 2.Kd4 Kc7?? 3.Kc5
2.Kd4 Kb7 with a draw (and not 2.Kc7?? 3.Kc5 when White gets the opposition and wins).
Black moved his king to a square of the same color as White's king (forming a rectangle with corners c7-d7-d4-c4), but White still got the Opposition and won. Doesn't this invalidate the rule given above?