There had been several things Karu could not tell Lind despite their many lifetimes together. For instance, she never knew how he appropriated her Talent's effects at all nor how changes were effected.
She also did not always know what he planned or what events occurred that never happened again when they were together. Lind had long suspected his former selves of intentionally hiding things.
He had 3 reasons for it. The biggest was the danger of undoing all the work. If Lind snapped back onto the path he was supposed to be on, the chains of fate would put him back on the path of certain doom.
Fate was being used by the Bastard to keep all potential enemies just strong enough to be useful and no more. The fact the Harmonic Dragons never existed before the current time line proved that alone.
