Continuing through The Worship of the English Puritans by Horton Davies:
The author gives some of his own appraisals rather than immediately quoting Durel, even though that is how he began his chapter. In Davies’ opinion, while the Puritans would invoke their own interpretation of Scripture in order to condemn, say, Calvin’s Church in Geneva when a difference was pointed out to them, they were ultimately ignorant of the greatness of the variance between their own convictions and those of the Continental Reformed Churches.
They would probably have been surprised had they realized the extent of their divergence from the customs of the Reformed Churches. They would have been even more amazed that, in certain features of her worship, the Established Church in England approximated more closely to the Reformed Tradition than they did themselves (p. 38).
The main point here was the use of written prayers, as opposed to only extemporaneous prayers, in public worship. Some Puritans, such as Richard Baxter, had no such scruples against using written prayers. But many did. Their influence is seen in the Westminster Directory, which Horton Davies says, “brought Puritan practice nearer to Calvin’s” (p. 39), but couldn’t actually include written prayers to be read in worship.