Yes your right from what I've heard
After the Radium radiation scare, ROLEX recalled many 6542 to rectify the problems quietly.
Part of the processes taken was to relume the Bakelite with weak Pm147 or Tritium lumes.
Pm147 has been around from the 50's so that would support your theory of Rolex using different radium compounds to lume the dial hands and bezel.