so ST 11 is another timeline [alt-reality]

[Set Harth]

doesn't mean any viewers should take that statement as dispositive

...again, because some people believe that's the way things should be.

if there are persuasive arguments to the contrary.

Unfortunately, they really aren't all that persuasive.

(Not to mention the whole revamped faux-Gregorian system of stardates, which apparently applies from the 2230s straight through to the 2480s...)

As for the 2480s, I have no idea what you're talking about. It is at least possible that the stardating system changed sometime between 2379 and 2387 in the Prime timeline, or prior to 2265.

 

[Kemaiku]

The Jellyfish states her manufacuring origin as "Stardate 2387".

Throughout the film Robau, Spock and Kirk all give stardates in the new style, 2233.04, 2258.42, and Into Darkness comes up with a caption "London Stardate 2259".

 

[Anduril]

Every episode is a different timeline than the previous one.