I actually just created my first PR from a sapling repo now - not sure why it’s not documented, but you can push your local development branch to a remote server, and in the case of github, you even get the “it looks like you’ve just pushed a local branch, would you like to turn this branch into a PR?” prompt, and it appears indistinguishable from a branch created with the Git CLI.
The message generated with the hyperlink for creating a PR is actually done server-side, you can customize any git server to do this, more or less. So yes, it should behave approximately the same assuming you can just do the basic push interactions.
Reading the documentation quickly, it looks like you can generate a standard pull request, it's just that the PR may not conform to expectations if there are multiple commits.
Of course, when it comes to github PRs, there are so many different "styles" of pull request, I'm not even sure which one should be considered "standard".
M4 Air should be in the spring.