Installing magisk with Android 11

Is there a problem with, or something missing from, the steps at this guide for installing Magisk on Android 11?

Specifically, in step 13, it says to flash the patched boot image (patched by Magisk Manager) to the phone, with

fastboot flash boot patched_magisk.img

followed by

fastboot reboot

And then to verify root in step 14 by checking in the Magisk Manager app. But doesn’t step 13 reset the phone, so the installed apps like Magisk Manager are also gone?