Lets start with 90.1(A), (B), (C). The NEC readily admits, it is not absolute safety, it is not necessarily efficient, it is not a design guide.
One of our posters made a particularly insightful comment - I'll paraphrase, "Saying that an installation is built per code means that if it were one bit worse, it would be illegal." One of my comments was, "No I didn't build it per code, I couldn't stand that level of un-reliability."
NEC is minimums - Might be okay for your house - generally it is way too light for industrial. For example, a recent poster was looking for advice on replacing burned up conductors on a 2MW (?) gen. He was really looking to minimize the copper because the cost of copper is high. I never got a chance to answer. I wanted to advise him, that minimums were not a good idea - minimums burned up once.
Now let's take a look at 240.21 tap rules and 450.3 xfmr OCP. Especially see 450.3, FPN 1 (NEC 2002). This stuff is some serious power, commercial buildings, industrial facilities, process power and control.
IMO when you are dealing with designs and installations concerned with tap rules and xfmrs, it is up to the designer to make it safe and reliable. The NEC won't save you or make you safe.
My design and build philosophy is to:
1. Make it so it will do the intended job.
2. Make it safe for the intended user.
3. Keep it contained so it doesn't crap up the environment.
4. Make it reliable to keep the life cycle costs down.
My theory is that if you do those four things, you are well past code.
The NEC is not a design guide. The AHJs are not designers. One size does not fit all installations. When an installation gets to this level (tap rules and xfmrs), the customer and the designer figure out what is important.