Microsoft announce that Windows 10 will update on metered connections. It’s unclear if the metered connections setting is currently faulty or if it’s actually working the way Microsoft intends and is downloading certain system updates. Regardless, the company will soon officially begin downloading some system updates while on metered connections anyway.
It’s likely that this is referring to extremely important security updates which usually aren’t too large and must be installed as soon as possible. It’s also possible that most Windows 10 machines already do this and the only change being made is that Microsoft is choosing to better communicate this function limitation with users to prevent them from thinking the setting isn’t working.