Guy Glantser does some explaining:
In the world of database management systems, ensuring data durability is of paramount importance. It involves guaranteeing that committed transactions are not lost in the event of unexpected failures or system crashes. SQL Server offers a feature known as Delayed Durability to address this challenge. Delayed Durability provides a mechanism for optimizing transaction logging and improving performance without compromising data integrity. This article aims to delve into the concept of Delayed Durability in SQL Server, specifically focusing on its behavior during expected shutdown scenarios.
Guy’s post surprised me, and I recommend reading it if you’ve thought about enabling the feature.