Yes. Previously back in OH 1.x, the Cloud Connector was a Persistence add-on and too many people used * (i.e. all Items) to be shared with the cloud and that caused all sorts of problems for the servers. So now no items are shared by default and you have to explicitly add each Item one by one to the config file.
How have you done this? My understanding is there is no way to share all Items in one go. You have to specify them all individually, either through the cfg file or through PaperUI. Are you confusing the cloud connector config with tags?
If you are using Official Google Assistant Integration for openHAB there is no need to select Items to share. You just need to add tags to the Items you want to control. Note that tags are not the same thing as adding an Item to the cloud connector config. https://docs.openhab.org/addons/ios/openhabcloud/readme.html
If there has been some addition to the cloud connector that I’m unaware of that lets you share everything then yes, all Items will be shared so all updates to all Items will be published to myopenhab.org. But I’m pretty sure this is not supported so I’m confused about what you have done.