I think maybe the point is that reading all your emails seems to be Google’s business model, while FastMail is a service provider that charges users for the service? Also, regarding “your data” being more secure with google... is more like Google is good at securing their main asset, which is Google’s data about you.

Google no longer uses Gmail data for targeting. No person or ai is reading your email from your grandmother, florist, or then confirmation that you bought paper towels on Amazon.