I agree. But the idea is not to pass it on any other third party for visualization. I feel Google Sheets will be comparatively more secure than other options out there.
That's true. Safer than giving your data to Intuit or similar, for sure. Google is very unlikely to analyze your spreadsheet to understand what it's about.
Is this sarcastic..? Sounds like something I would especially see Google do.
There are plenty of people for whom adding their expenses to a Google Sheet offers little reduction in privacy. For those people, the statement is accurate.