Upgrading refers to "upgradability validation" which is not defined

[runephilosof]

heads-wiki/Installing-and-Configuring/Upgrading.md

Line 149 in dcd3bf6

For migration instructions, refer to the [Downloading documentation]({{ site.baseurl }}/Downloading) and ensure you follow both the upgradability validation and integrity validation steps before flashing.

But Downloading.md does not mention upgradability validation.