You are half right. Holstered anywhere in a vehicle is OK. Plain sight unholstered is OK. Unholstered in a glovebox or center console box is OK.
Under the seat unholstered, under a coat unholstered, etc is NOT OK.
To understand the maze, you must understand the legislative intent, and their goal to balance personal rights with LEO safety. The concept is that a reasonable person should expect that an item (ie: gun) could/should be in a container that is being opened; An overt/obvious act (opening the case) is needed to retreive the weapon. A holster covers the same basis; the gun must be accessed and removed from the holster. Plain view is plain view; If you don't notice a gun on the front seat, you've got more problems that just that.
A gun, unholstered and under the driver's seat, for example, is surreptitious, and therefore viewed as dangerous.
There is no codified 'two-step' process for firearms in vehicles in AZ, as some think. But with that understanding, the legislative intent bares close resemblance to a 'two step' process for non-plain view guns.
I am not saying I agree with the lawmaker's intent, I am just explaining it.