First of all, please note that we are now at version 8.2.2 since the question was first asked.The corresponding menu and screen options have changed a bit here.
As far as I can see in the short videos, they are part of the Tour Videos and not from the actual Masking Tool itself.
When in the Masking Tool you have the Options which Tool you want to use. After that it downloads the Option that can take some Minutes and in that time it shows those short in-between video Sequences to pass the time while waiting. After that the Tool itself works perfectly. As you can see in the Screenshot I already have downloaded one of the Options. Hope that helps.
You can update Lightroom to the latest version to use these features. If you face any errors while using the feature, please share screenshots and more details about the issue.