well this is my theory on how the torrent training method had such huge impact on Yang Guo.it states in Lanny's excerpts of ROCH that the gallbladders opened up all the accupoints points clearly so chi could flow though clearly, this allowing YG to breathe easier and as most wuxia is written that internal energy is accumilated through breathing exercises and controling the circulation of chi so this would allow Yang Guo to accumilate interanl energy faster because there is no hinderance due to blocked or not very clear accupoints. the torrent allows to utilize Yang Guo's internal energy in a way similar to QKDLY but it is in practise similar to someone studying at school for a qualification and someone working on the job and gaining experience like an apprenticeship. again in lanny's excerts it tells us that when yang guo first goes into the torrent that he has to utilise his chi in different areas to withstand the torrents and in athena's translation of the 3rd edition of ROCH on YG's training in the ocean that how the waves attack from every direction and YG has to circulate chi to maintai balance. THis also strengthens his internal energy similar to how muscle development works as in once layers of muscle are worn out then new layers are created to further strengthen the muscle. With the gallbladders clearing his pressure points it maximises the effect of the torrent training. in battle YG can utilise his chi effectively to swing his sword and yet maintain and use his internal enrgy as he has used the sword to practise in the torrent.
this is just my theory on it if anyone wants to discuss it or share their own theories that would be welcome