What matters is tire pressure while you are riding, not cold pressure. Most ST riders aren't super aggressive, so 42 psi cold would typically mean 45-50 psi while riding (depending on ambient temp and your riding style), which seems like the sweet spot. If you are going to take your bike to a race track for a day of fun, you can expect very warm tires, so I can see why you would lower the cold pressure to e.g. 36 psi. You would then take it easy on the first few rounds until the tires have warmed up and pressure is in the mid/upper 40's as I described above.
I took my FJR to a track last summer, and the first thing they did was to take air out of my tires. I have a TPMS, and I can confirm that my rear tire reached the upper 40's which I'm used to during normal riding.
