...officials are working to get a remotely operated vehicle that can reach a depth of 6,000 meters (about 20,000 feet) to the site as soon as possible.
The 5-person submersible, named Titan, is capable of diving 4,000 meters or 13,120 ft. “with a comfortable safety margin,” OceanGate said in its filing with the court.
but...after looking up on Wikipedia
I think they’re advertising the depth limit of the recovery vehicle, not claiming that the wreck is actually at 20,000 feet.
They probably need quite a bit of margin too if the craft accidentally got lost in a deeper area
Maybe they're concerned that it no-clipped through the sea bottom and wound up deeper than the Titanic's current location?
It might be best practice to use a vessel rated for considerably deeper than you actually go, in case of some problem in the hull?
And/or it's just a description of a particular vehicle they're bringing that was most convenient to get there quickly.
It's not like they're going to say, "oh, don't bring THAT recovery vehicle, it can go TOO deep."