I know it is a Christian belief. There is no way to prove the premise so it is an article of faith. Don't try to paint it otherwise.
The premise of your topic is
Christian-based....at least, that's how I understand it.
I gave an article that explains bibliolatry from a Christian site (as compared to your source, Wikipedia).
Your OP asks how many Christians practice bibliolatry - how can we really have an answer to that if we don't know exactly what bibliolatry is?
And, how can we tell exactly what bibliolatry is if we don't delve into the Christian perspective?
To have a rational answer to your question - we have to know exactly what is bibliolatry.
It's a very logical response, isn't it?
As Christians - If we believe the Bible is God-breathed.....and if we believe God does not tell lies.......then, we have to believe the Bible is the Authoritative Book that God has given to mankind!
Surely - when you buy some electronics, it comes with its own manual that tells us information about it - including how to care for it, and what not to do with it, right?
Aren't we supposed to follow that manual? What happens to our refund policy if we don't?
If we follow the manual diligently - does that mean we place more importance to the manual than to the company that built the product? That's the simplest analogy I can think of - which everyone can relate to.
By the looks of it, bibliolatry is just another word being thrown around by those who don't believe the Bible is the AUTHORITATIVE "MANUAL."
In other words, some think we can add or "re-package" certain parts of the Scriptures that we don't agree with! Maybe, they want to conform with the changing times!
Some even came up with their own Bible - like, The QUEEN JAMES Bible!
Well - God's stipulations don't change! They are as consistent as they were given eons ago, even as today! And, Christians are required to be steadfast!
Changing anything from the Scriptures is similar to pharisees who kept adding their man-made rules or ideas to the Scriptures! Changing anything from the Scriptures is a big no-no! Several verses stipulate that!
Rev 22:18-19
I testify to everyone who hears the words of the prophecy of this book: if anyone adds to them, God will add to him the plagues which are written in this book; and if anyone takes away from the words of the book of this prophecy, God will take away his part from the tree of life and from the holy city, which are written in this book.
Deut 4:2
"You shall not add to the word which I am commanding you, nor take away from it, that you may keep the commandments of the LORD your God which I command you.
Proverbs 30:5-6
Every word of God is tested; He is a shield to those who take refuge in Him. Do not add to His words Or He will reprove you, and you will be proved a liar.
Mark 7
6 He replied, “Isaiah was right when he prophesied about you hypocrites; as it is written: “ ‘These people honor me with their lips, but their hearts are far from me.
7 They worship me in vain; their teachings are merely human rules.’
8 You have let go of the commands of God and are holding on to human traditions.”
9 And he continued, “You have a fine way of setting aside the commands of God in order to observe your own traditions!