Are new macOS versions retained in the recovery partition?
Found the answer to my own question:
The simple answer is, whenever you perform a major OS X upgrade, the Recovery HD partition is also upgraded to the same version of OS X. So, an upgrade from Lion to Mountain Lion will result in a Recovery HD linked to OS X Mountain Lion.
source: https://www.lifewire.com/identify-os-x-version-on-recovery-hd-partition-2259968
Josh, it is even better: as soon as you want to (re)install OS from the recovery partition: it installs the actual OS version including the latest update: for example you have 10.12.3 on your mac and you install OS from the recovery partition, it will install 10.12.6