I see way more files in my mapped Google Drive dir in Ubuntu compared with what I see when I use the Google Drive web app. These extra items are also not in my "Shared with me" folder in the web app.
I was seeing exactly the same - hundreds of files and folders in my Google Drive when viewing with the Ubuntu Files app, but when I looked at Google Drive using a web browser, they weren't there. They also weren't in the Google Drive Bin, and neither where they shared with me. Eventually, I worked out why. If I disable Show Hidden Files in the Ubuntu Files app, they all disappear. I suspect that Google Drive must just "hide" files if they are moved or deleted from anything other than their web interface. I think all the files that I could see before I disabled Show Hidden Files were probably deleted from the same Google Drive folder in my Windows PC.