No, it's mostly a matter of scope of the claim.
It would be just as difficult to prove that they were diving for 24 hours a day, every day, for the last year, as it would be to prove they were NOT diving for 24 hours a day, every day, for the last year.
Similarly, it is just about as easy to prove that "sometimes they are diving" as "sometimes they are not diving".
Granted, it is easier to prove that "sometimes they are diving" than to prove "they are never diving." But it is also easier to prove that "sometimes they are not diving" than it is to prove "they are always diving."
As you can see, the degree of difficulty has nothing to do with positives or negatives.
Another factor is access to the proofs. It would be easier for DBPE to prove they are actively recovering artificats than it would be for a random message board poster to prove that they are not, simply because the company has access to th proofs. Simiilarly, if they were NOT recovering artifacts, the company would be in a better position to "prove" that, than a message board poster would be able to "prove" that they were.
Again, this has nothing to do with positive or negative.
One exception is in tryting to prove that something does or does not exist in a large space. In that case, it MIGHT be eaiser to prove the positive than the negative. If I assert the existence of unicorns in the world (without ready access), and you assert that they do not, it might take me just as long to catalogue everything in the world until I came up with a unicorn as it would for you to catalogue everything in the world to prove that none of them were a unicorn. Or I might get really lucky and bump into one as soon as I walk out the door to look, whereas you would still need to catalogue everything in the world.
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