The article isn't about removing all traces of Google from your site/stack. It's about removing 3rd party tracking from your site. Specifically, it focuses on removing Google Analytics.

Using Google Sheets doesn't add 3rd party tracking back in. Even if you don't trust Google to not take a look at your spreadsheet, it's unlikely anybody or anything at Google would treat your spreadsheet like analytics data.

All that being said, it is a little funny seeing them funnel the data right back into Google. Personally, I would also prefer a different storage method.