Sometimes it’s hard to see the difference between a patronymic and a middle name.
One of my ancestors, Hendrik Jan Smulders was called “Jan” because his father was named Jan. At that time, people in Tilburg didn’t use a genitive form to indicate patronymics so it’s difficult to see if “Jan” is a middle name or a patronymic. In other regions and times, the name might have been Jans, Jansen, Janssen, Janse, or Jansse, which more clearly define it as a patronymic.
Another situation where a patronymic may be hard to recognize is if the base name ends with an -s. For example, “Hans” can be both a first name and a patronymic. Studying the other names in the area should show if middle names and patronymics were used. Throughout much of Dutch history, middle names were not common, and a “middle” name could well be a patronymic.