That is actually not true. Whale falls exist so it's entire conceivable that bodies fell to the bottom intact and never refloated. In fact we have a couple photos of the wreck that indicate that some bodies did make it all the way down (there's a photo of two shoes side by side where a body landed, and everything else was eaten away but the shoes remained). Your buoyance as a human corpse is largely driven by a combination of the air in your lungs and post-death gas release. But at certain low temperatures and pressures (found in deep ocean), the death and pressure removes the air from your lungs, decomposition slows down significantly so there's no gas release, and thus you sink instead of float. The cold and pressure would actually in a vacuum do a better job of preserving your body than you'd think.

There is however no chance that any skeletal remains exist unless there's a room on the titanic that somehow miraculously was not flooded since the ship sank (no evidence to suggest this is true, but it's technically possible) , because anywhere water can get fish, crustaceans, and microorganisms that consume every single part of a human body can get. Some organisms can eat through bone. Organic material (bodies, wood, etc) was eaten away by ocean life long, long before the wreck was discovered.