Google has changed the way that app indexing is handled on Google Search and is now showing any available related apps instead of just ones you already have installed.
Apps have been indexed in Google Search for quite some time already, but today Google has made some changes to the way it displays results. Previously, Google Search only showed the option to open results into apps that you already had installed on your device, but now they’re are opening that up to apps you haven’t installed.
Source: iMore