Delayed durability - can data loss be prevented in case of crash This book suggests that 
"Data loss is possible with delayed durability because you might lose committed transactions. If SQL Server crashes after a transaction commits, but before the 60KB buffer is filled, that transaction cannot be recovered because it is lost."

However wont the transactions be available on the transaction log and can be replayed for recovery?

https://books.google.co.in/books?id=5Es3DwAAQBAJ&amp;pg=PT159&amp;lpg=PT159&amp;dq="data+loss+is+possible+with+delayed+durability"&amp;source=bl&amp;ots=Mwmh4cKa6G&amp;sig=tctRb18itYQyBxo7lLhkT1w4-z4&amp;hl=en&amp;sa=X&amp;ved=2ahUKEwjAyau784jeAhWHMo8KHW1XCi4Q6AEwAHoECAEQAQ#v=onepage&amp;q="data%20loss%20is%20possible%20with%20delayed%20durability"&amp;f=false
When you enable delayed durability, transactions aren't written to the transaction log file before they are committed.

That's why transactions aren't available in the log, and they will be permanently lost in that scenario.