Yes, a Web VR can be created and can be shared on Facebook. To achieve this follow below mentioned steps:
1. Create Web package (Package without "Export as ZIP for Hosting yourself" - keep it unchecked).
2. Click on "Open Hosted Page" under "Download" section and copy the link from browser address bar.
3. Open Facebook, Login to your account and create a post.
4. Add above copied Web VR link and submit the post.
5. You will be able to watch the tour like below on your facebook page as shared.
Note : You can also customize Tour's Title, description & Image in InstaVR Dashboard >> Web >> Social path prior to publishing WEB package.