In One Piece Green: Secret Pieces it is written that Blackbeard was originally supposed to be so strong that he was even unbeatable by the Marine Admirals.
In the original setting for Blackbeard’s power, Oda did make him very strong. In his early design, Blackbeard was unable to feel hot, cold, pain or even numbness. His only weakness was being unable to swim.
Taking this information into consideration, the Editor who wrote the Databook just assumed that maybe Blackbeard could even take out the three Admirals with his powers..
Another interesting thing is that Marshall D. Teach was originally named as Everything D. Teach. This name may come from 17th-century English pirate Henry Every, famous for becoming the richest pirate in the world at the time and getting the highest bounty in history placed on his head.
Dubbed “The Arch Pirate” and “The King of Pirates” by contemporaries, Every was infamous for being one of few major pirate captains to escape with his loot without being arrested or killed in battle, and for being the perpetrator of what has been called the most profitable act of piracy in history.