Well, this was actually a real concept, albeit one that never got past the initial idea.
It's likely they were deemed incompatible with the darker, more mature tone that Starbreeze/Machine Games wanted to take the series in. Their absence is particularly noticeable since almost every other major memorable enemy from Return to Castle Wolfenstein, including the Black Guard and Uber Soldiers, make an appearance.
Wolfenstein: The New Order is the fourth entry note sixth if you also include Castle Wolfenstein and Beyond Castle Wolfenstein in the Wolfenstein series, developed by MachineGames, a studio founded by several key members of Starbreeze Studios (developers of The Darkness, Escape from Butcher Bay, and Assault on Dark Athena) who left in 2009.