Sushi-grade isn't a thing! It's marketing. I also doubt this follows the FDA rules for flash freezing that sushi grade implies given the lack of risk for parasites.
Source: ex-commercial fishmonger
-4°F (-20°C) or below for 7 days (total time)
-31°F (-35°C) or below until solid, and storing at -31°F (-35°C) or below for 15 hours
-31°F (-35°C) or below until solid and storing at -4°F (-20°C) or below for 24 hours
With ground beef recalls left and right, we fortunately live in an age of avoiding large-scale liability.