This is not a California thing, it is a Federal thing. The EPA tests the truck in the "default" configuration. If the auto-start-stop could be disabled and stayed that way the EPA would have to test the truck in that mode, defeating (at least in the sticker ratings) the purpose of having it.
There are a variety of ways to override this feature, and several lengthy threads on it on these forums. The most "OEM" like (but certainly not the least expensive) I have found is this one (
https://www.autostopeliminator.com/.../products/2015-ford-f-150-autostop-eliminator ). All of the other techniques had some advantages (for example, many are less expensive) and disadvantages (many are semi-permanent or require modification), but this one acts like it should have from the factory, it remembers the last condition you told it to be in, on or off, and when the vehicle is restarted it is in that last commanded mode.
T!