At one time they did not meet any US standards. I cannot find anything on your link that says they do.
IPC Code sections.
. Prefabricated showers and shower compartments shall conform to ANSI Z124.1.2
, ASME A112.19.2/CSA B 45.1
or CSA B 45.5
. Shower valves for individual showers shall conform to the requirements of Section 424.3
424.3 Individual showe
. Individual shower and tub-shower combination valves shall be balanced-pressure, thermostatic or combination balanced-pressure/thermostatic valves that conform to the requirements of ASSE 1016 or ASME A112.18.1/CSA B 125.1
and shall be installed at the point of use. Shower and tub-shower combination valves required by this section shall be equipped with a means to limit the maximum setting of the valve to 120°F (49°C), which shall be field adjusted in accordance with the manufacturer's instructions. In-line thermostatic valves shall not be utilized for compliance with this section.
Also your shower drain is sized by the amount of body showers and shower heads .
Shower (based on the total flow rate through showerheads and bodysprays)Flow rate: Trap Size
5.7 gpm or less 1 ½ Greater than 5.7 gpm to 12.3 gpm 2 Greater than 12.3 gpm to 25.8 gpm 3 Greater than 25.8 gpm to 55.6 gpm 4