I guess I thought they were referring to the wreck (noun) as opposed to the wreck (verb). Damn nautical terms. If they meant the verb, then they should have worded it "The wreck couldn't have happened any earlier than that date".
Although, I agree - the wording was confusing. I had to read it twice, myself.
And the conclusion is false - the civilian divers may have found the actual wreck (noun) and treasure (noun) elsewhere, and planted the bell (noun) and $50 in gold on this unrelated wreck (noun), and reported it to the government (expletive), in order to distract the busybodies (nannies), while they mined the real wreck (money) for the actual treasure.
or maybe not.