Plain Style elements are short sentences, the use of concrete words over abstract ones, and the use of an author's native language.
The first sentence of History of Plymouth Plantation contains eighty-nine words. Therefore, it does not adhere to the defining characteristic of using short sentences.
As for the use of concrete words over abstract ones is not necessarily justifiable either. Given the fact that the first paragraph contains words such as "godly", "judicious", and "breaking out of y lighte of y gospell" the language certainly does not adhere to the use of concrete text over that of abstract.
Perhaps the only characteristic of Plain Style that the text does adhere to is the use of the author's native language. Given that William Bradford was an English leader, his diction and style mirror that of his native England.
Therefore, based upon the characteristics of Plain Style, the text the History of Plymouth Plantation only meets one of the features characteristic to the form.