>>72473573https://youtu.be/cDXCTmQzAak?t=4928Here is a stream from a year and a half before New Underworld Order where she clearly refers to herself as THE grim reaper.
Her bio was changed to THE grim reaper at some point between April 5th and May 8th, May 8 is more than 2 months before NUO, and also her original bio never said apprentice, it reads as follows.
> What is up, humans!? Calliope Mori(森 カリオペ)-HoloEN’s Rapping Reaper!ホロライブEN>>72473585yes