Desktop's behavior is also often useful to me where it auto-fills the PR title/comments with information from the commits in the branch. I'm not sure what the algorithm is there though.
It does it if there's only one commit iirc. If there's more than one, it only fills in the title with the branch name. I usually don't use it because of that.
I find it quite useful, and I've been missing it when working with the new 2.0 RC. I agree that the template would be useful also. Not sure how the two could be combined...
We're currently ignoring PULL_REQUEST_TEMPLATE.md and .github/* files in the PR creation form, and we should use templates to pre-fill the description, if the templates exist.