I want to add an email form to a wordpress site, but all of the existing ones I see are from third parties. Doesn't Wordpress offer an official email form to add as a widget or block?
No. There is no official email form block or widget.
JetPack is not "official", but is developed by the same people who run WordPress .com, so it is as close to an “official” block that you’ll get, even though they are not the official developers of the WordPress software itself, and you’ll need to install a plugin and connect to a WordPress.com account to use it.