Performing an upgrade of the database
pg_upgrade does not copy WAL, nor pg_log, nor any random cruft you put in the old directory which is not under PostgreSQL's control.  Use something like du -sh /var/lib/pgsql/data/* to see where the space is actually being used in old and new servers.

Why is still showing the old data directory and not the new one?

It is showing you the files which are being copied from old to new.  Why should it show you the name of the destination, rather the name of the source?  The latter seems more natural to me.