How does al-Nawawī present al-Shāfiʿī’s views on a guardian fulfilling an obligatory fast owed by the deceased?

All Shāfiʿī scholars agree without qualification that it is valid
It is treated as wholly identical to voluntary fasting in all cases
No disagreement or different view is reported from al-Shāfiʿī
There are two views: the famous one denies validity, while later critical Shāfiʿī scholars prefer the view affirming it