The fact that, despite how violent he poses himself to be, Ratbeard had no intent to kill his old crew
coupled with this line from a scrimshaw side quest
Paints a surprisingly consistent image of how Ratbeard treats other- specifically YOUNGER- pirates.
The only time we ever had combat with Ratbeard was cut from Bad Company, I assume so it didnt take as long since he runs off a few rounds in regardless, so now it gives the in-universe impression that the reason he never engages us is because the main character is obviously a kid. He likes younger pirates, possibly because he's an old timer and wants to see the 'industry' continue on. It's surprisingly present in his character
edit: esp since his background gives me the impression he was young when he screwed over Fowl and it led to his injuries and his fathers death. Ratbeard doesn't want to be someone else's Captain Fowl. (But Lasko...kinda makes him into that anyway)