The Eleventh Floor was something that Azekiel had never seen or heard about, even in his last life. They all knew that the element Floor existed, but none of them knew before what it was like or what was going to be there.
By the time Azekiel had died in the last timeline, even the Kings who were in the lead had only been on the tenth floor at most. They hadn't managed to get to the eleventh Floor, so even they didn't know what the eleventh floor was like, let alone Azekiel.
It was only when Azekiel was at the door of death that he was informed that the tenth floor was cleared.
He didn't know in the past about the eleventh floor, but it looked like he knew some things about it now. That's why he was able to describe the eleventh floor to Raphael to some extent, addressing it as the place where the real tower of Sin began.
Through the portal on the eleventh floor, Azekiel stepped out. Raphael and Lia came out of the portal after him.