Many things change with MV, MH, and HPS lamps across the 150W line, which I call the 150W Dividing Line Of Stupidity, or DLOS.

First let me explain why I make this distinction. In most <600W HIDs, there are three different ranges of voltages that the arc usually runs at. This is just due to practicalities in lamp design. Here they are:
- 45-55V: American and Japanese low voltage HPS lamp standard
- 85-110V: European/other country HPS lamp standard
- 130-145V: International MV lamp standard
Of course note that lower wattage MV lamps run at lower voltages than their respective voltage class but just stay with me.

Let's start with the objectively more sane system, the European/other country standard.
- 85-110V HPS lamps
- 130-145V MV lamps
- Metal halide lamps exist for both standards (meh)
Alright everything looks just fine and dandy, let's go to the North American system.
- 130-145V MV lamps (great so far)
- 55V <150W HPS, 85-110V >150W HPS (aaalrighty not great but manageable)
- 85-110V <150W MH, 130-145V >150W MH lamps (ok eww)

Correct me if I am wrong, but I believe the North America arrangement was made like so:
- 130-145V MV standard adopted cause it works well on 240V chokes where 240V is accessible
- 130-145V probe MH standard adopted, but with higher OCV autotransformer ballasts (introducing the definite need for a step up autotransformer for the convenience of keeping voltage standards and compatibility with MV)
- 85-110V adopted for HPS, despite us not using 240V choke ballasts (could've chosen 130-145V with a higher OCV autotransformer ballast just like we did with MH but whatever, we were just copying other countries I guess. A mistake IMO)
- 55V adopted for <150W HPS (mixed feelings, it has pros and cons, IDK)
- 85-110V adopted for <150W MH (complete mistake, absolutely should have used either the existing MV standard or existing low voltage HPS standard)

Am I getting the order or this correct? I just want to understand why choices were made the way they were. Not that it makes any difference. Does anybody know more about the history of this?

Everywhere the objective is practically the same: Get the total cost of a given light quality as low as possible. The mains voltage and the way the lamp performance deteriorates if you move its specs away from its optimum at the given power (so results to more expensive light) and the scale each chemistry was used meand it made sense to unify some lamp specs world wide or to separate others according to the mains voltage at the given market.