While I think the test will be informative, the point of the TPM is the same as the oil level warning.
The bigger issue for me is what is the best pressure to set the tires at for tire life and road holding. I will then set that pressure at home with my accurate gauge, plus one pound, then head out on my long ride, confident that unless there is a problem, the tire pressure is "in the hunt".
For the manual to indicate that 42 psi is the be all, and end all, for all conditions, seems like lawyer speak to me. We each need to determine the pressure that we like best for our riding style, motorcycle loads, and tire model. What would be nice is if we share our favorite pressures with the forum.