This is expected behavior. You will see installs for any device that you have in your Devices list in your App Gallery account even if they are installed by another user. The only way to not see this is to remove that specific device from your devices list.
When I am logged into the XAG and click on My Apps, I may see an App, in this case "@printbyxerox", as being installed by someone else on another device. I have attached a screenshot of what I am seeing. Is there a fix for this? I have cleared cache.