Actually that is part of NEC codes. On the service disconnect there is supposed to be sign saying it has an ATS/genset and directions to generator and disconnect at the generator with sign noting disconnect inside here. All gens are supposed to have emergency shutoff. There are several internet write ups on wire sizing, label, offsets etc. Even an example of a Sarastoa. The all have to be bolted down to concrete
It was my understanding that what you said only applies if the generator is permanently wired to the transfer switch. If the MEP is not a permanent install and wired through a plug that can be detached then that wouldn't apply.
Looking at the 2011 NEC the only thing similar to this I could find is
NEC 445.1 Disconnecting Means.
Generators must have one or more disconnecting means that disconnects all power, except where:
1) The driving means for the generator can be readily shut down,
and
2) The generator isn’t arranged to operate in parallel with another generator or other source of voltage
NEC 702.7 A sign that indicates the type and location of on-site optional standby power sources must be placed at the service-entrance equipment.
I found nothing concerning any type of emergency shutdown required, only that it must be able to be disconnected.
I know there is a 2014 version, and possibly newer than that, but it tends to take utilities a few years to adopt a new set of standards from my experience.
I will say that very few of the automatic backup generators I've worked on (I repair Generac standbys for a living) have any type of obvious markings for where the disconnect would be, as the majority of them are installed either as a replacement breaker panel with the main disconnect at the top, or are installed as a sub-panel. The ones that I do see that are service entry rated still require removing several bolts in order to access the panel and the disconnect.
When my own personal equipment got inspected, I had an electrician friend install a complete new electrical panel, wired it for a 30 amp inlet and interlock kit. Utility company came out in the morning, pulled the meter to disconnect power, and came back in the afternoon to reconnect. They came inside and took a quick glance at the panel/wiring, and liked what they saw. The actual inspector didn't come out to check on it until 3 days later and also had no issues with the panel wiring or interlock setup. I don't recall if he even glanced at the new power inlet box on the outside wall, and my generator wasn't anywhere in sight.
I have yet to see any of these generators in the consumer side of things that have any type of emergency shutoff. The commercial level units do, but the emergency shutdown is still inside the unit at the control panel, most of the time they require some type of key in order to access.