As I stated, most records are created the way WM created his, randomly and naturally, as opposed to deliberate and multiple attempts to break and document an existing record. I have no idea who held the record, or what it was, before WM ran his 526, nor do I think that it matters.
Just for the sake of conversation: I don't believe that inclusion in the Guinness book is a requirement of having, holding, or breaking a world record. The person wanting inclusion in the book, which was first published in 1955, must submit his application and certain documentation, which does includes video, to the publisher, and they do have some very sensible requirements for the new record to be validated.
Link:
https://www.guinnessworldrecords.com/Images/GWR-Evidence-Guide-2018_tcm25-486431.pdf