Has this been done to avoid any last second confusions in the transfer market because of the Club World Cup? Because this means that as soon as the Club World Cup started, clubs can essentially get into negotiations with players that are already playing in that competition. They can't of course transfer them and use them in that competition, but there have been plenty of transfers or contract extensions now that were aiming at getting players in right before the competition starts or give them short period contracts like 1 month to still have them available for this competition and then they can leave and go to their new club or sign new contracts with whomever they want.
That is good point about Club World Cup timing. Letting clubs talk to players during tournament could really help make transfers smoother and less chaotic later on. This way clubs might not need to sign players to quick short deals just for competition. Instead of this they can plan for long term getting commitments from players while they are still playing. This seems like it would make transfer period after Club World Cup much more organized and calmer for everyone involved.