I didn't say the Holy Spirit was restricted to only speaking through Scripture. Isn't it logical that when Jesus was speaking to His Apostles telling them that the Holy Spirit was going to teach them all things and bring to their remembrance ALL the things He had taught them, that He might have been talking about their role in writing the Scriptures since what Jesus taught them is recorded within it? They didn't have recording devices back then or shorthand. These writings, like the sacred Scriptures written and preserved by God through the Jewish people, are given to us by God as a more sure word of prophecy and testimony. They are our authority because they came from God. It is why the precepts of our faith are found within them and whatever is presented as necessary for our salvation and life of faith must be proved by them.
Good.
He might have been talking about their role in writing the Scriptures
Of course, but He also said that the Paraclete will abide with the apostles forever (John 14:16), so the operation of the Holy Ghost, while includes His role in dictating the scripture is not limited just to the creation of the scripture.