It's a method to increased his internal, but doesn't mean he didn't use DG9J. He could have easily executed the breaking moves while wielding the HIS, making it much more effective than just using basic swings and counting on sheer force to down the opponent. This might work against opponents with low to mid level internals, but against someone like SM or XZ etc it won't work. How will be undefeated if his internal is not as high and HIS was just some basic moves?
Well any of HIS or DG9S could make you "invincible" even without superior inner power unless you meet someone like Xiaoyao Elders level fighters or higher so there is no need for Dugu to "combine" HIS with DG9S also if HIS could "match" with other sword arts End-ROCH Yang Guo would not use ordinary sword to perform Jade Maiden with Xiao Longnu during great battle in Xiangyang the other reason is HIS rely on "power" while DG9S on "technique" and "agility" which make it even more harder to "combine"..
So not novel reader here but from each serial adaption does lhc after leaving huashan n before learning the absorbing move does he use any internal when executing 9recluse?
Even when fighting fengbuping I thought he wasn't able to use any internal so all his sword moves Is just from 9recluse n the wall art sect breaking skills?