The source says Baba's advice was mainly ethical and he didn't give discourses on the Upanishads. How could his teachings be considered profound or beneficial for achieving ultimate welfare if he avoided deep philosophical subjects?

While it's true that Maharaj did not openly explain profound Vedanta subjects or give discourses on Upanishads, his method was strategic and deeply beneficial. As Chapter 0 explains, his primary approach was to first purify the disciple's ground with ethical advice before sowing the seed of knowledge, which is a traditional practice for a Sadguru. He would satisfy the worldly desires of his devotees and then seamlessly guide their minds toward ultimate welfare. The most valuable guidance came not from open verbal advice but from the direct experiences devotees had with him, which provided the highest benefit to those who approached him with faith.