Iode is based on Lineage and its just the same process. So instead of re-writing the same they just refer to this. 7.1 is a new Android Version and not just an update.
How to Upgrade?
For devices running iodéOS 6, you’ll need the iodéOS 7 Updater app to upgrade. Download it here: Updater-v6-to-v7.apk. You can also find a download link to the Updater app in our latest news via the iodé News app. iodéOS 7 is Now Officially Available! - iodé
Put the point is, why iodeOS info message leads to lineageOS