If Declan were more eloquent, he may have explained the not needing sleep in regards to health restrictions. It was simply that Guardians could run themselves to death if necessary. It didn't mean they didn't get tired. Only that per their general immortality, they didn't strictly need it.

Fortunately Aoba was spared that grim topic.

"Well," he murmured, pressing the heels of his hands into both eyes with a groan. "I was thinking, maybe your Chosen Ones going all over the universe and time and space were trying to keep it fairly quiet? Or the study of the phenomenon was kept under wraps because places like Clovis Bray and the like would try to manipulate the knowledge and use it themselves. There's lots of reasons it could potentially be in there. It's worth checking, if I can."