Ok, I looked at the site where this is written and it is word for word verbatim. I don't necessarily agree that it is "complete [censored]" though... here is a demonstration of how you can add on additional seals (at least two), in this case, thus verifying the claims made by the seller.
Note carefully that the watch is inside a hermetically sealed jar; additionally a zipper closure seal is added over the jar rendering the watch sealed with two extra water tight seals. The watch is now ready for pressure testing. Note well that I have carefully placed the sealed watch within the confines of a sink. However, I am quite certain that the watch would pass any water proofing tests I could perform in my home so I ceased with this demonstration. I conclude that the first part of the claim made regarding waterproofing, "Additional seals are add on," is valid and true.