Here's a comparison of nickel and ball curvatures on a 13 MM tip (enlarged for clarity).
A tip with a curvature anywhere near that of a ball would be far too flat. In order to reach the miscue limit without playing on (or past) the edge of your tip you need at least 60 degrees of arc in the tip's curvature - you get that with a nickel or dime shape, but with a ball shape you can barely reach half that far before hitting on the tip's edge and risking miscues.
pj
chgo
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1) "Very near" and "nowhere near" are subjective terms. Stop being a pedant, anyone who knows the game well uses rounded tips, not flat tips.
2) Speaking of subjective, place the edge of the nickel in your diagram at "A" touching "B" so that it's top sits atop the ball's equator . . .
. . . and we'll see you are stretching the truth, and . . .
3) We all avoid using the edges of the tip anyway, near the miscue limit.
4) I wonder how many books Bob owns that advocate shaping to a nickel coin? But what do pros know? And countless strong amateurs shape to a nickel. You consistently tell everyone you know more than the pros.
5) If I looked at your cue tip now, it will almost surely sit somewhere between a nickel and a dime shape, depending on preference. So give us a "break" (pun intended).
--Thanks for the correction on the curvature at any size tip. You are certainly correct. Now play nice with the other children today.