Out of all of human history, and some history of the heavenlies, and out of all the words and deeds prompted or committed by God, the Bible contains those God considered necessary.
It does not surprise me that God’s Word is handled in a variety of ways by a variety of individuals. Hasn’t it been that way ever since Eden?
And again ... that doesn't really answer the question of what you mean by that.
It's fine to say "necessary," but the term "Bible ONLY" would tend to imply not just "necessary," but also sufficient.
A "necessary and sufficient" viewpoint says that the only place to find God's word is in the Bible ... and thus the Holy Spirit loses importance. That's what the article is talking about and rejecting.
"Necessary" says that you cannot dispense with the Bible as a source of God's word; but it means that we cannot take the Bible as the sole source: we must look to other sources as well. This view is in accord with St. John's description of the Holy Spirit: will teach you all things and(D) bring to your remembrance all that I have said to you (John 14:26). One implication of this view may be that God may speak "new words" to us that may be also accepted as authoritative. But because the Bible is "necessary," the new words cannot contradict what's already in the Bible. Note that Scripture appears not to place any particular end date on the work of the Holy Spirit, however -- a view which could suggest that it's still possible to add a book to the Canon of Scripture.
"Sufficient" says that we can find God's word in the Bible and trust it, but that it's not the only place we can find a trustworthy exposition of God's word. One might suggest that St. Paul was saying something like this in Romans 1:20, his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made....
Again, you can see each of these at work in the various religious controversies.
It's probably not right to break it out so cleanly into these three categories; I can find something good in each of them, though I suppose I tend more to the "necessary" one more than the others. I'm curious which of them you would see yourself fitting into.