I mean really. Just take almost any category of beer and look up its history. Its real history, and there is usually nothing that resembles the modern description,, but yet the modern description goes out of its way to include a historical description of processes and ingredients.

Steam beer requiring Northern Brewer hops, yet those hops were not even in exsistance when this style was at the height of popularity.
Stouts requiring Roast Barley and/or black patent when at the time that stout were defining themselves roast barley was illegal and black patent again, was not invented. Not for about 100 years.

What is the reason that well known styles with well known histories that are so easily researched, have such inaccurate guidelines?

As with most every other part of beers history, it probably had some political implications. Both legitimate and back room.