HG says that :
Guru tatva and Shiva tatva are the same.Like how the guru aids the student to reach Sri Krishna, so also Lord Shiva aids a devotee to reach Lord Krishna.
There is an account of how Skanda was asked by Lord Shiva to learn from Brahma. Brahma sends him back saying that Skanda answers/counters all that he is saying, and he wants to learn the meaning of Omkara at the beginning itself. Skanda asks Lord Shiva the same, and Shivji Himself smiles and says that he doesn’t.
So Skanda asks Lord Shiva to place him above Shivji’s shoulders, as Lord Shiva had asked Skanda to explain Omkara to him, and he could do that only him only if he was given the status of Guru.
So if in terms of tattva, Lord Shiva and guru are identical, then Skanda should have been on equal footing with Lord Shiva,apparently contradicting what HG said.