Board Thread:Questions and Answers/@comment-5693502-20140510161053/@comment-16674955-20161231212316

Baekryun was already a ranker when Urek was climbing the tower. Urek heard about the forest of Baekryun and visited him then they became friends and Urek would regularly visit him, in between floors test or after he became a ranker himself.

By the way, SIU did say that the team was climbing the tower really fast but it's because he doesn't want to drag it too much or probably doesn't want to create timeskips right and left.