Yes, reference 10 jumped out at me as well. I thought personal correspondence references typically include one of the authors of the paper.
https://scholar.google.com/scholar?q=W.T.%20Tutte%2C%20Perso....
Sloppy scholarship. On the other hand, it's simply a credit attribution of posing the problem, so it's not material in evaluating the results. I observe that the majority of references I can find that attribute this to Tutte are very indirect - i.e., citing sources that themselves claim Tutte was one of the people who formulated it - so it would take someone with a little more time on their hands (or perhaps an LLM) to track down the original...