iOS 13.4.1 was originally released a couple weeks ago, but one iPhone model is just now getting it today.
Apple today released the iOS 13.4.1 update for the new iPhone SE. Spotted by MacRumors, the release of this update suggests that the iPhone SE that's being released tomorrow will be running iOS 13.4 out of the box and so new owners will have to update on day one.
Included in iOS 13.4.1 is a fix for an issue where devices running iOS 13.4 couldn't participate in FaceTime calls with devices running iOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier. It also fixes a bug with the Settings app where choosing Bluetooth from the quick actions menu on the Home screen would fail.
The update to iOS 13.4.1 is a small one, but it's important to be running the latest software available to your phone so that you've got the most up-to-date bug fixes and security patches. And so if you're getting an iPhone SE in the near future, be sure to check for this update after you get your new phone set up!