An interesting thing that I have noticed about Japan's HID lighting portfolio is that virtually all of their 1000W mercury vapor lamps are apparently electrically identical to the North American low voltage 1000W H34 mercury vapor lamps instead of being electrically identical to the North American high voltage 1000W H36 mercury vapor lamps despite the fact that both North American countries and Japan have low domestic mains voltages where Japan uses 100V mains while the North American countries use 110-120V mains. However, I have seen that the North American countries have discontinued the low voltage 1000W H34 mercury vapor lamps and ballasts much earlier and opted to use the high voltage 1000W H36 mercury vapor lamps and ballasts instead due to the fact that 1000W H36 mercury vapor lamp/ballast setups were said to be more efficient than the older 1000W H34 mercury vapor lamp/ballast setups when considering autotransformer ballast circuits. Even though Japan has commonly used 100V autotransformer ballasts for many of their HID lamps, I am wondering why Japan still opted to use the low voltage 1000W mercury vapor lamps instead of designing high voltage 1000W mercury vapor lamps despite their higher efficiency.

Here is an example of a spec sheet for a typical Japanese 1000W mercury vapor lamp:

https://www2.panasonic.biz/ideacontout/2014/09/23/2014092300130150.PDF

Additionally, here is some information about a 100V HX-HPF autotransformer ballast specifically designed for the Japanese low voltage 1000W mercury vapor lamps:

https://www-iwasaki-co-jp.translate.goog/lighting/support/products/detail.php?ItemNo=H10TC1A71&_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=sc

It is the power of an "inertia of a standard". Once something becomes standard, there has to be very good motivation to go for something else for the same function.
The H34 format came very likely first, so set the standard.
Now when the H36 came along, the "1kW MV" market was set and stable, but not that big. So once RD money was invested into the H34, there was not enough incentive to invest into the H36 system.
The thing is it is not only "just another lamp and ballast type", it means creating also some measures to make sure the lamps won't get mixed up, so coming with some marking system, educating all the technicians and also dealing with consequences of the mixup errors. The benefit of the limited use base was just not justifying all the hassle with introducing an extra lamp type (having the same the "1kW" rated power label would definitely lead to mixups; see the mess with all the "400W MH" types in 230V market).
Also in the meantime other technologies came around into the pool, with way stronger benefits (higher efficacy, better light control so optical efficiency,...), so if someone would want to depart from the H34, he would likely go for one of those than with just marginal improvement of the H36.
So they stayed with just what they had.

Plus when in the clear form, the low voltage offered shorter arc, so better optical efficiency when beam forming optics was involved, so somewhat compensating for the lower efficacy of the lamp alone.