I wouldn’t make that assumption. Any content aware service will flag that content.

Google's ToS state otherwise.

> Our automated systems analyse your content (including emails) to provide you with personally relevant product features, such as customised search results, tailored advertising and spam and malware detection. This analysis occurs as the content is sent, received and when it is stored.

https://policies.google.com/terms

All Gmail content is scanned. If you get spam filtered, it means your email is scanned. They certainly aren't going to opt their paying customers out of looking for child porn either. And I'm pretty sure their Smart Compose/Smart Reply features are also trained on everyone's mail, G Suite included.

The only thing Gmail has ever said they won't scan G Suite customers' email for is ads, and they don't do that with consumer email anymore either.