Quoted from toyotaboy:
To get the optimal manufacturing yield from our cabinet vendors, the cabinet was made slightly shorter. This also met a request from our European operators to make the pinball footprint smaller while delivering the same Williams pinball feel everyone knows.
Optimal manufacturing yield doesn't have anything to do with the monitors though. They determined that they could save money by shrinking the playfield slightly. I believe in Tilt, they talk about how they did this because it allowed them to make a cabinet out of one piece of wood instead of two or something to that extent.
Also, I always find the argument that the games play so much differently because of this 3" size difference to be a strange argument. Look at the picture that you attached. While the RFM playfield is clearly shorter than T2, neither has shots at the very back of the playfield that you're hitting, nor do most games out there. T2 has targets on the lower right closer to the flippers than RFM does. The center targets on RFM are higher up the playfield than they are on T2. T2's right ramp starts closer than either of the ramps on RFM do.
I'm not saying by a long stretch that T2 sucks -- my buddy has one and I LOVE it -- but it clearly illustrates to me that the geometry of the actual shots isn't changed, just the length of the playfield. If anything, it makes the games play faster than they had been, something that to me is a win