The original developer of Git is Linus Torvalds and he wrote it for the use of developing Linux. He handed off the project to Junio Hamano after a short while who still leads it. They use a process where you submit patches by mail, for Linux and for Git itself too.

To make this easier they have the commands git format-patch, git send-email and git applymbox later changed to git am to apply them. They also added git request-pull to generate a short plaintext email like message to request a pull.

The Pull Request as a bigger concept of data and discussion that should be kept around came from GitHub and was put over top of Git. The concept has been rebuilt by various competitors separately. But it doesn’t match the Linux and Git development model so they never used GitHub Pull Request, even though there is a GitHub mirror of Linux and a GitHub mirror of Git. For them the discussions happens in the mailing list.

So it’s very unlikely they would start including the stuff that was added by others over top, that they don’t need.