Patrick,
The ball on the green stimping at 12 will travel at a faster speed over the course of it's roll out.
That's the fundamental concept behind the stimp meter.
Really, that's the fundamental concept! Who knew. Have you ever used a Stimpmeter? Have you ever measured the speed of the ball as it rolls out the 12 feet? At which point in its travel did you measure the speed?
There is no stopwatch involved. There is no measurement of the ball speed. You simply raise the bar to 20 degrees and the ball releases from the notch and rolls along the green. You measure how far the ball went in feet and inches and that "distance" is the stimp reading. The stimp reading gives no indication of how fast the ball was rolling. The Stimpmeter reading give no indication of the speed of the ball at any point.
For your information, the initial velocity of the ball coming off the Stimpmeter is around 6 feet/sec. When the ball stops it's velocity is zero. In between it is decelerating due to friction between the rolling ball and the turf. On a green stimping at 6 (feet) a ball will decelerate faster than on a green stimping at 12. So, if premise is that a ball coming off a Stimpmeter rolls faster on a fast green than a slow green, that would be correct as soon as the friction between the ball and the turf kicks in.
But, that's a silly premise. Nobody putts with a Stimpmeter. And no intelligent player is going to hit a 20 foot putt, or any putt, with the same force on a fast green and slow green. In the real world, on a slow green, you'll stroke the ball harder to go 20 feet and it's initial velocity will be higher. On a fast green you'll stroke the ball softer and the initial velocity will be lower. The velocity will dissipate faster on the "slow" green, but for a good portion of the 20 feet it will be moving faster than a 20 foot putt on a "fast" green. Of course, if you can provide some empirical evidence to the contrary, I'd be happy to see it.
On your "case for fast greens" I'm not surprised that you like them. They favor more skilled players such as yourself. The USGA discourages green "speeds" over 10 (feet) because they are too hard for the masses and slow down play.
For me, I like fast (10 feet) greens with undulations although they humble me sometimes. My home courses are both high speed and highly contoured. They contribute significantly to slow play. Our men's nights often run to 5 hours because of the difficulty of the greens. So, it's a blessing and a curse.