The article specifically states that it is not including small groups (cells within a church). So while I see your point, I would say that the author would differ in opinion.
But what does he mean by saying that it doesn't include "cells within a church," when he also states that the overwhelming majority of house-church members ARE, in fact, active churchgoers within a non-house-church church? Is he excluding only those organized by the church leadership within a given parish? Are Cursillo/Emmaus/Chrysalis groups counted? How about charismatic prayer meetings? Ecumenical praise meetings? Non-parish-based Young Adult prayer meetings?
Does a house church, by definition, include a pastor, minister, or anyone with some formal training? Do they have any rites which set them apart from mere prayer groups? Or have we simply dumbed down the notion of church so far that people are thinking of mere prayer groups as churches?
The very fact that the author claims that only house churches are biblical shows that the author has a fantastic ability to warp facts to his liking; the early Christians convened in houses because they were forbidden by Roman law to purchase church buildings; that is, until "power-mad" Constantine legalized Christianity.
If he's claiming house churches are more biblically authentic, do house-churches have annointed leaders? Presbyters? Episcopi? Do they partake in the Lord's Supper together?