Not long after Li Yuanba left the belly of the mountain, he switched to "Step by Step Lotus"; in such a perilous environment, he needed to conserve his Spiritual Power to respond to any potential dangers.
He maintained his Corpse Refining state and did not switch to his human form.
He needed a safe place to be able to switch to the human state, knowing that his current Corpse Refining state had reached the middle stage of Silver Corpse, and it was not just the beginning of that stage.
Once he switched to human form, his Taiji Dao Body would automatically balance the cultivation between the Corpse Refining and human states, and he would face the advancement to Golden Core in his human state.
Furthermore, the Body Refinement realm of the Silver Corpse was somewhat peculiar; he did not know what changes there would be in his Body Refinement when he switched to his human form.
If something major happened and he encountered a spirit beast, he would be in trouble.