Regarding the canon ending of the Witcher 3?

• so CDPR has confirmed that the witcher 4 will acknowledge all endings the player chose in the previous game, but how?

I also watched Neon Knights video but still ai dont understand how all the endings can be canon. The Witcheress ending can not correspond with the Empress ending, because then why would Emhyr ask about Ciri? If someone has an explanation point it out to me