We don't even know what "them" was referring to, they might've said "them" because they figured out Teach was there with his crew and not alone.
Marco said Teach has an abnormal body, so Teach managing to eat two fruits isn't as surprising to Marco, after all Teach doesn't even sleep, still Marco had absolutely no idea how exactly he used two fruits simultaneously.
In Imu's case however, the only question is does King Nerona Imu exist? Yes or no? Did Ivankov just baselessly make up that character?
Marco said Teach has an abnormal body, so Teach managing to eat two fruits isn't as surprising to Marco, after all Teach doesn't even sleep, still Marco had absolutely no idea how exactly he used two fruits simultaneously.
In Imu's case however, the only question is does King Nerona Imu exist? Yes or no? Did Ivankov just baselessly make up that character?
Right so there are factual possibilities explaining why Blackbeard was able to do what he did, therefore it isn't actually a mystery by your logic.
Ivankov suggesting they could be the same person is a theory, not a fact, Ivankov himself even considers the logic a "wild leap" and uses words like "coincidentally" and "maybe", these aren't confident claims backed up by facts, they are ideas being thrown at a wall and hoping something sticks.
