But, reasking the question.
If there is functionally no difference between LG and CN, what's the point of alignment? It's not even descriptive at that point because the descriptors are meaningless if opposite descriptors can apply to the same thing.
Where I do find it interesting is in alignment archetypes. Wolverine makes a pretty good CG archetype, I think we'd agree. But, what's a chaotic neutral archetype? The only one I could think of was Q from Star Trek. And, well, everyone keeps telling me that CN is totally reliable and completely okay with working with groups, so, Q obviously isn't CN by that standard.
So, what character would you see as being typical of a CN alignment?
"If there is functionally no difference between LG and CN, what's the point of alignment?"
Is anyone here other than you claiming there is no functional difference between LG and CN?
So, going with one of your recent cases - on watch - itsbperfdftly gone for a CN to be very reliable on watch duty, if that is any part of personal history, for instance. Perhaps the CN is born out of a history where such a tragedy was involved. (Indirectly perhaps) and so now this charscter actively avoid responsibility and despises authority in favor of folks looking out for themselves but when it comes to them bring forced into such roles- in those rare occasions, they do do reliably.
Imagine if you will a tragic tale where in a crisis a community or group listened to bad authority and relied on them to provide for safety only to have that authority prove incompetent or corrupt with tragic consequences.
Imagine one person coming out of that with "screw authority, everybody take care of yourself" who actively avoids positions of responsibility or authority and never relies on official or authority - views them all as default as incompetent or corrupt as that tragic day. This person might well be extremely reliable when they do have to take on such tasks. Thry might take on scout roles so that they don't work as often depending on others.
Imagine another person coming out of the same case who saw it as the failure in authority that leads to the disaster, not that the folks followed, but that the authority failed them. To that person, becoming a beacon of authority that can be seen as competent, non-corrupt, etc to help honor and restore people's faith in order or institutions is key. That person seeks out cases and opportunities to take on authority and obligations- especially when they see cases of corrupton or incompetence again, trying to prevent the repeat tragedy. They may try and help build up or replace - depends on situation and means
The former could easily be CN or anywhere on the C scale depending on other aspects and beliefs. The latter could easily be LN or LG but even LE depending on choices and beliefs and methods.
So, there you have a case of some event producing very different characters on opposite sides of the alignment spectrum for law snd chaos but neither is " unreliable" as far as taking watch or necessarily performing s task they agree to take. The huge difference is one Avoids taking much responsibility and lives in a way that shows "self-reliance and take care of yourself" but the other seeks and takes on responsibility at most every chance and lives to show the value in that.
This kind of division between C snd L is far more common in actual rpg play than the view put forth that C or CN means taking a watch in life or death threat and whimsically doing something else.
To me, you will find a whole lot of folks who agree (usually after bad alignment conflicts with GMs) that LG (or LN) is **not** "lawful stupid" and frankly that holds just as strongly for the C-side not being C-stupid as well.
But again, I find it odd that I am someone who jettisoned alignment in 1e and who played many many other systems where alignment never stained their system pages st sll, yet I am here defending the non-extreme alignment position.
If extremes help your gsme, that's great. To me they fo have value at times but not at the point that you get yourself putting do much of your " options" painted in extreme corners.
Seems to me that a GM eho enforces and reinforces their own notion of "chaotic must mean unreliable" has basically painted thst whole C-side as mostly out-of-bounds for PCs as really one things many parties and small squads will avoid like the plague is unreliable when it matters.
If that helps your games, great.