> They could also be talking about specific queries, e.g. with Chrome's default settings, the address bar can answer some queries like weather or calculator using search without having to press Enter.

I'm almost certain it's this - that was added in Chrome 69 [0] which was released ~7 months prior which lines up with the email thread.

[0] - https://venturebeat.com/business/chrome-69-arrives-with-reva...