The 35 million number seems to be from a recent Taxpayer Advocate Blog (June 29th) that said as of the tax deadline (May 17th) , there were 35 million.

So it seems like the news media just grabbed that number, despite the fact that numbers seems to be outdated.

https://www.taxpayeradvocate.irs.gov/news/nta-blog-2021-filing-season-bumps-in-the-road-part-iii/