Kass has said multiple times that his mentor is dead. His mentor is also a castle bard and not a sheikah researcher. That's an absolutely ridiculous theory.
If you watched to the end, he'd explain that he knew about that gap, but my personal idea is that after Robbie claimed to have failed Link, he started fresh and "died" as whoever he was. This would explain him being a Bard as well
Kass has said multiple times that his mentor is dead. His mentor is also a castle bard and not a sheikah researcher. That's an absolutely ridiculous theory.
It has more problems than that.
There's also the fact that the Sheikah in the memory and Robbie look nothing like each other. The only thing connecting the two is skin color (which is weak evidence). He also tries connecting him to Kass via Robbie's "guitar riff," which is also weak evidence since Kass plays the accordion. The fact that there is no evidence of musical scores or lyrics in Robbie's memoirs or anywhere in his lab weakens this theory significantly. You would need strong evidence if you're going to casually call someone as good-natured as Kass a liar concerning his mentor's death.