RFB 2.0 thread link below, 1st post number 18 explains what they've done.
18. Lookout specialization re-named to Quartermaster. In reality, petty officers with the Quartermaster and Signalman ratings drew the duty of 'Quartermaster of the Watch' and were assigned to bridge detail. (Source: The Fleet Type Submarine). In addition, the Signalman rating was absorbed into the Quartermaster rating twice in the post-war era (1948 and 2003).
https://www.subsim.com/radioroom/sho...d.php?t=159709