Needing to navigate a menu to set title and description as it seems to show in the screenshots seems like completely unnessecary friction.
The thing I like most about it in a little use today, though, is when it goes to create the PR, it lets you choose to create it directly, or open a 'preview' of the PR in the browser. This is nice for creating Draft PRs which you're still working on and should not yet be merged (since, right now, there's no way to create a PR then put it back into 'Draft' state).
> exactly the same mechanism as git uses for "git commit"
That's not how git commit works. git commit opens $EDITOR and makes a list of lines (sans commented-out lines) from that. The first line being a title is only convention, whereas in a github PR it's a formal element of the system.
If you don't format your commit messages properly then they'll just be a sloppy mess in any email-based workflow (like what Linux uses).
And the first line is the only line that's displayed in contexts like `git log`, so it truly is the commit summary even if you aren't emailing commits.