Over a month after the release of macOS Sierra 10.12.4, Apple quietly let slip the news that it changed macOS Recovery modes, including the startup key combinations used to enter them. Full details are given here, in a Knowledgebase article dated 3 May 2017.

If your Mac is running a version of macOS/OS X prior to 10.12.4 and supports Recovery mode, the available modes and their reinstall behaviour remains unchanged:

• start up into local Recovery mode using Command-R, and if you reinstall macOS you will get the same version as is currently installed on your Mac;
• start up into remote Recovery mode using Command-Option-R, and if you reinstall macOS you will get the original version which shipped with your Mac, and will then need to update that to any later version.

There are now effectively three different Recovery modes, which behave differently depending on whether your Mac is running…