Can't take credit for any such quote. But, I did day that nitpicking is a good thing.
Some lines on a football field do not have a vertical component, i.e., extending the ball or part of a body over the space above the ground outside of a sideline means nothing. However, by rule, and with the respect to the ball only, the goal line is treated as a plane, i.e., when the ball touches or penetrates (in whole or in part) that plane, that means something (could be a TD, could be a safety, could be touching/batting of the ball in the end zone).
For the purposes of a field goal, the goal is treated as a "line," thus, requiring the ball to touch something (not merely penetrate a plane, as in the case of a TD) to determine if a goal is scored. In theory (never seen it happen, even in windy west Texas), a FG attempt could pass over the crossbar and between the uprights, but get blown back thorough the uprights and over the crossbar, and it will NOT score.
As to the question about the ultimate height of the uprights (or the inside edge, at least), #92 is right in that the rules don't directly address this condition. However, the fact that the physical criteria for the goal, by rule, requires the uprights to be AT LEAST 30' above the ground implies that, if taller uprights, with no limit on their height, are allowable, then the inside edges of the uprights must extend vertically to infinity.
Robert