The problem being: that "line" is 60 yards from the goal you are facing, but only 39 yards and 8 inches from the goal you are defending.
The 50 yard "line" is actually halfway between the edges of that 4" wide stripe that everyone sees as the 50. If the goal "lines" are exactly 100 yards apart, and the major yard "lines" are marked 10 yards from each of those lines going toward the middle of the field, it would be impossible for the 50 to be either the right or left edge of the actual 50 yard "line". By definition, the actual 50 yard "line" would be down the middle of that 4" white stripe in order to be 50 yards from either goal line.
OK, for most purposes, this is "close enough". The one exception is a kickoff. If the 40 yard "line" is the goal line side of K's 40, and the field is marked as described above, 10 yards would be the MIDDLE of the 4" wide stripe designating the 50, not either edge.
Good luck calling that one. For all practical purposes, if the ball touches any part of the 4" line that designates the 50, it's gone far enough. And who can say it didn't?
OK it is winter, there's way too much snow on the ground and more expected, so I'll bite. With the firm understanding that this is "Much ado about nothing", allow me to question your logic. I hope we agree that a properly marked field is 300 feet BETWEEN 2 (goal) lines, which would place the dead center of the field 150 feet (1800 inches) between those lines.
NF: 1-2-3-j, advises, "Each goal line mark shall be entirely in its end zone so the edge toward the field of play and its vertical plane is the actual goal line" (and therefore the boundry from which the 300 feet is measured).
NF: 2-26-5, further advise, "The LTG is the
yard line established when a new series (1st down) is awarded. .... the LTG is 10 yards in advance of the foremost point of the ball when placed for the first down of the series".
NF: 2-24-3, "A free-kick is any kick which
puts the ball in play to start a free kick down......".
NF: 2-7-1, "A down is action that starts with a legal snap, or when the ball is kicked on a free kick".
NF: 6-1-1(a), "K's free-kick line is: (a) Its 40-yard
line for a kickoff".
So, in essence, the 4 inch wide stripe(s) at 10 yard intervals across the entire 300 foot football field, are simply 4 inch stripes (essentially designed for esthetics and administrative assistance) they are
NOT specific "Lines" for measuring purposes designating exact distances.NF: 2-25-1, The line of scrimmage for each team is a
vertical plane through the point of the ball
nearest the team's goal line. It is
determined when the ball is marked ready for play....."
You might consider that in effect, there are actually
duplicate 20, 40 and 50 "yard lines", each specifically measured from the goal line each team is defending, outwards.
The game of football has long been played under a "general
PRESUMPTION", that all marking lines are actually straight, squared and properly marked, that has served the game well since its inception.