Classified information.
Should we also disregard Wernher von Braun's disclosure in the 1970's publication of Popular Science talking about crashing a Saturn rock stage into the surface? (Apollo 13 mission) - linked above.
Or should we believe the 2016 publication in Space.com showing the impact crater, from the Apollo 16 mission, from an S-IVB rocket stage?
Moon Mystery Solved! Apollo Rocket Impact Site Finally Found
Or should we just believe the official NASA disclosure in 2006 that doesn't even talk about von Braun's disclosure or rocket impacts and go with your reference for the Earth as well as the Moon? - linked above.
"Between 1969 and 1972, Apollo astronauts placed seismometers at their landing sites around the moon. The Apollo 12, 14, 15, and 16 instruments faithfully radioed data back to Earth until they were switched off in 1977."
"Furthermore, shallow moonquakes lasted a remarkably long time. Once they got going, all continued more than 10 minutes. "The moon was ringing like a bell," Neal says."
Withholding classified information doesn't equate to "no reason to believe his story". Assuming that you've reviewed the evidence provided and done some research on operation Highjump, I would think that most people would believe that his story is genuinely true.
His diary is even more intriguing when you get into the history of it.
Not just any old sailor...Navy Admiral.