Yes totally possible. The emails only came from one email address and was totally anonymous (so didn’t appear to be multiple people). You can read all the email contents as they have now been published to Facebook:
ScubaSam
What I can say is our writer (Michael Menduno) actually spoke at length over video conference with the people behind the emails. He also spoke at length with a number of other people involved with the record including Gabr, as well as previous record holder Nuno Gomes and officials at Guinness and Netflix (as there is a documentary apparently being completed about the dive which Gabr is closely involved with).
We know who these “scuba Sam” people are and they are very reputable sources who were very close to Gabr and the world record dive.
Michael spent nearly 3 weeks researching the articles and interviewing widely.