It's to flash the TCU. Newer firmware and codes should improve the transmission reaction/ drive-ability / reliability. Early batches of proton CVT from punch was plagued with jerks and so hence there's so called CVT reflash done on most sagas. Normally, if there's is no problem with the current firmware, there is no need to reflash it to a newer version. Some time there's just some glitch in the coding which they've fixed but ultimately there's no change in gear change characteristics. TCU tuning is nitch, I know a few people who actually can tune TCU for CVT but it's more geared towards daily driven setup. If you're good in TCU tuning, you may increase the number of virtual gears or lock the gearbox to change at peak power rev. You will not over rev your engine unless you're at over drive / neutral / reverse