This is a pretty bad article in a number of ways. An awful lot is assumed (and, I think, wrongly so) and it does seem slanted toward belief. I skipped over some and gave up.

This article is extrapolated from Azim Shariff and Will Gervais' Templeton foundation sponsored study "Accurately Measuring Religious Belief And Attitudes Around The World" 2019 via the University of British Columbia.
Azim Shariff has since cut all ties with the "Templeton Foundation" not so Will Gervais, who as evidenced by this article is still associated with said organisation.
The John Templeton foundation, for those not familiar with it, is a " philanthropic organization that reflects the ideas of its founder, John Templeton, who... "wanted to support progress in religious and spiritual knowledge, especially at the intersection of religion and science." at least that is what it says on their foundational documentation.
In reality the Templeton foundations promotes religious fundamentalism, undermines atheism and its notorious "Templeton Prize" given each year along with a LARGE cash prize has gone to among others
Mother Teresa (1973) genocidal maniac, friend of dictators
Billy Graham (1982) Spiritual Advisor to the Whitehouse
George Fielden MacLeod, Baron MacLeod of Fuinary (1989) founder of the Iona Chrisitian isolationist Community on the island of Iona.
Carl Friedrich von Weizsäcker (1989) a German theoretical physicist who worked on Nazi Germany's atomic bomb program.
“Bill” Bright, (1996) president and founder of Campus Crusade for Christ International
King Abdullah II of Jordan (2018) Self proclaimed 41st-generation direct descendant of Prophet Muhammad and "Most influential muslim" in the world and untaxed proprietor of a secret "vast empire of wealth that he disguised through offshore companies and tax havens"

" the Templeton Foundation ... blurs the boundary between science and religion and makes a virtue of belief without evidence.
Richard Dawkins,

I do agree with the article that some atheists claim to be intellectually superior. I am not one of those atheists.

I also agree that relying on self-identification by atheists will result in less than accurate numbers. Many people go along to get along.