Hmmmm, I'm not familiar with the legend, but it does lend credence to another old expression, "What goes around, comes around", eh?
FGS
It’s not only part of the King Arthur legend, it’s a very common component of many “hero” legends...the great hero dies protecting his people, but his love and dedication are so great that he will come alive/wake up if they are ever threatened again. It’s a common meme.