Office 365 is the only version can have future office version and new feature update or upgrade. That is Office 365 selling point.
Installation Office version, setting is by default accept automatic update. If you don't want Office 2016 or Office 2019 update, no point to install Office 365.
There is no way to stop update to Office 2016 or Office 2019 when installation Office 365. If you choose not connect internet when you install Office 365, and change automatic install to no update allow in Office 365 setting. Then reconnect internet. It still show Office 2016. Why? It is because Office 365 in the market very long time, Microsoft save buyer time, now office 365 in the market, even download from Microsoft, is with office 2016 together.
If you insist just want Office 365, I can tell you Office 365 is not better than Office 2016.