Question is, how do you prove that claim jumping was intentional? They easily could have just discovered it on their own, and been the first to sell.
I know of only one instance when a specific body was deliberately sniped from EDSM, and even there, the evidence was that the guy pretty much boasted about it. Oh, and another where the guy said that even though he got the body specifically from EDSM, he was the first discoverer because the tag on the body now says so.
But yeah, as far as I know, not only do various clients have the option to hold on to uploads until you dock, but also EDSM itself has the option to withhold until that, or a month has passed. Still, if there's something you're worried about others sniping, best not to upload until you sell the data - or if it has already happened, you can always beeline to the nearest base. (The farthest you can be from any base is now, what, 40k ly?)