St. Philip is an apostle, certainly not "some man" and certainly he was filled with the Holy Spirit. This is why you need the apostolic Church to understand the scripture.
No, you need just the Spirit
If a pharisee had happened along, and the eunuch inquired of him the meaning of the scripture, he would have gotten a very different answer, although this man would have claimed to be an authority. You have no way of knowing if what a man teaches is true, unless you yourself have no discernment.