The Monster's Manual.
What you've missed is that this alignment discussion is completely pointless and has nothing at all to do with the original arguments or their points.
It is at best a failure of understand by you how it is not important, and at worst an obfuscation attempt in order to avoid the real issue.
The argument I was making was that you should (or could), make two sides different from each other, so that working for one will provide different adventures and different a different game than the other.
You seem to be arguing from a side of "no, the two sides the players choose from should always be identical and give the exact same outcome because I really want to deny my players any chance of having an impact on their game".
Hell, even two normal equally moral grey human nobles could (or would probably) have different types of land and different types of economy. So working for one side would involve protecting valuable mines from intruders whereas the other would involve protecting farms. Or whatever difference you want. Two sides being absolutely equal except for the color of their tabards is just cartoonish.
Forget the moral stuff and focus on the discussion we are having; there is no reason at all why two sides should be identical and that working for them would result in identical adventures.
Except, apparently, that everyone has the same culture.
Glad we established that.
Unless your world is just One shade of grey, even in a grey world, no group is just as likely to betray the characters as any other group. People are DIFFERENT, some are more loyal than others. That's the thing with shades of grey. Some people are more loyal than others. And if the players happen to work for a more loyal person, the outcome in the game should be different compared to if they worked for someone who is disloyal.
Do you agree with that or do you think that both all people are equally likely to do any action always?
Except your example has a problem in that it is not, in fact, good to imprison someone whom have acted on your orders just because you intentionally didn't give them a writ only so that you could later imprison them. It's not a good act by any measure.
Using one example to highlight how a game could be different depending on the choices made is perfectly valid as it invalidates the argument that "no the game is always identical no matter what the players choose". The only counter argument is "I don't care about established NPC personality or verisimilitude or anything, I would never let the players make any choices that turn out to have meaning and the whole game is solely run based on my whim".
Sure, but this Grey Game discussion is really not the point of the Agency discussion. It's an unimportant sidetrack.
Either something is very possible and does randomly just happen OR it is rather unlikely and would never randomly just happen. You can't both have your cake and eat it. Choose what you want to argue for.
So how often has it happened in your games that a Storm Giant with Greater invisibility has cast Lightning bolt on the enemies of your players? Ten times? A hundred? Exactly how common is this? Since you say it is "very possible", it must have happened more than once and certainly along the lines of 10% of the time.
Yeah, but which action? How can I select which action to take if I have no possibility to judge which is most likely to lead to success? Based on your "anything might happen" argument, I could either 1) Hit with my weapon, 2) Whistle a lovely tune or 3) Do the Hokey-Pokey and regardless of which way I go, anything might happen. So my enemy might take damage or they may not.
Either actions are divorced from their consequences or there is a link. Which way do you run your games?
In my games, hitting an enemy with a weapon is more likely to kill them than whistling. Your preferences can be different, but then you really shouldn't be in a discussion about player agency because your whole premiss is "I don't allow it".
No it can't. I can't be the president of USA, I can't survive standing in the middle of nuclear bomb explosion, I can't upload my consciousness to a computer. There are plenty of things that can't happen. It has never been, nor ever will be, "anything can happen". That's not how Real Life works.
Except that those details are really important, and can make the difference between life or death.
But they will do different something.
As I said above, it's not a thing they do if the crimes are ones they've ordered themselves! That's not part of the idea of "good", even if it is a Grey Game without an alignment system. But this is a tangent also and we should drop this discussion as it has very little to do with the point that players making choices can affect the game in meaningful ways.
Does that mean that if all of us suddenly started to agree with you, you would change your opinion?