I have never seen that in any "codes". In fact, you are more likely to find a code that requires the spout to be a certain distance above the drain/rim, and require an overflow for a spout that is not limited in GPM. If you look at the design of the shower, you will see that it requires you to be inside the shower, in front of the shower head to turn it on. You can not reach in from the side to turn on the water. Therefore, the first bit of water that is still cold when you first turn on the water would be a bit shocking if it didn't have a way of warming up without spraying you.

Yes, I am a professional builder with a thorough knowledge of codes. Even way back before mixers were required.., and a tester of any kind was never required by any nationally recognized model codes.

If you can't give me a year and code number, then you should probably just drop it or admit you are wrong.

Most people just turn the shower head away before turning it on. They have never required padded walls and grab bars in the shower either :D

It is not required by code:) It was a personal preference of my client as mentioned in the numerous answers if you scroll down in 'more info' section. He simply wanted to test the temperature before turning on the volume control, he could have easily turned the head away too:) I find it fascinating that this little detail has sparked so many queries on this photo!