The test named for carrying the durability verdict to the system widget asserted only has('system'), and system is an unconditional key of the render array -- the controller's own comment beside storage_durability says as much. So the assertion could not fail.
Confirmed here by deleting the line that supplies the verdict: the new assertion fails with "Property [system.storage_durability] does not exist", where the old one stayed green.
Test-only, no application code.
Reported and fixed by @denkfabrik-li.
Ignacio Nelson
b16d780ebe