the PGA Tour has a device to measure green firmness and they use it to test each green multiple times per day to try and make them consistent.
Maybe I'm getting old, but wouldn't the game be better with more variability of conditions? The whole "play it as it lies" thing? I get that you don't want one green to be super fast and another slow. But if you cut them at the same height, why isn't that enough? If one green is exposed to the sun and wind and another is protected, by the end of the day, wouldn't you expect the exposed green to play faster and firmer than the protected one? Isn't that part of the fun of the game? A battle of wits with mother nature?
Maybe this is what I like so much about links courses. The imperfections and inconsistencies. The bad bounces and hidden bunkers. The variability.
You mean judgement,experience and course knowledge?
The forgotten skills..
Nowadays most skill is gained in the gym-or so they tell me.
One of the attractions of golf is that it is an outdoor game, yet so many are trying to modify the training, the playing, the teaching, and the conditions to that of an indoor, perfect minimal variable "experience".
As you said, precisely why many of us enjoy the links, but even they are not immune to the phenomenon.
The Thumper has been around awhile-the USGA was using it at The Bridge during the 2010 Mid-Am.
Regarding two kinds of firm-I'd say thatch plays a huge role.
I'd bet you could get the same Thumper reading on two different greens, yet one would repel shots more than the other if it had less thatch.
Gregg Stanley went years at when he first arrived at The Bridge not aerifying the greens in an effort to develop more thatch.