Github probably considers the "depth" of git use by the average user to be one of its KPIs. Git is extremely powerful, if you are only doing checkouts and commits you are under-utilizing the tool and also underutilizing the service. So it's smart for Github to build tools that lower the bar for a) understanding git, and b) using git's more powerful features. Useful metrics would be things like the percentage of users…
But then you start talking about pull requests, which are not a feature of git. They are specific to github (e.g. try finding a PR comment in the git repo).
Does the new tool help with advanced git stuff, or does it just serve the github workflow?