«...forget about it, would you?»

What if Guizhong
last words were actually a prompt  for
Zhongli to unlock «Memory of Dust»?

«This is the mark of our pledge, and it also my challenge to you»

«All my wisdom is hidden within this stone dambbell»

<…>

«As for that stone dumbbell, forget about it, would you?» 

Her lesson
for him was to learn to forget, to move on, to change. 

I imagine that all of
this is very hard for Rex Lapis, who quite literally is an embodiment of stone.

But for him it was the only way to  become more human.

It took him
centuries to finally say good bye to her by arranging her funeral. And while
people of Liyue were mourning Rex Lapis, Rex Lapis was mourning Guizhong.

I can
imagine that after all this (letting Guizhong go and giving away his gnosis) Zhongli
is finally able to unlock  «Memory of
dust». Maybe it even unlocks by itself - all magical seals that held it secrets just
disappear.

But
when Zhongli touches the dumbbell, it crumbles to
dust. Empty.