As you noted, it is a quad dominate movement.
It is a good Auxiliary Exercise for the Deadlift. Gene Bell, one of the great Deadlifter of his era, was ask it helped his Squat.
Bell replied, that if helped is Deadlift more so than his Squat.
Deadlift Quad Drive
Both the Conventional and Sumo Deadlift require quad drive.
In the Conventional Deadlift (Research Dr Tom McLaughlin) the drive off the floor is initiated with the back, then the quad fire. It is like a one-two combination in boxing.
The Sumo Deadlift is initiates the drive off the floor with the legs with assistance from the back.
Thus, increasing Quad Strength is vital for the Conventional and especially the Sumo Deadlift.
Deadlift Lift Leg Press Assistance Training
The Conventional and Sumo Deadlift are performed from a Quarter Squat Position. That means the most effective method of preforming the Leg Press for Deadlift Training is to preform them from the same Quarter Squat/Leg Press Position; this eliminate the back issue.
Conventional Deadlifters will increase quad drive for by performing Leg Press from the same medium to narrow width stance as their Deadlift.
Sumo Deadlifter will increase quad strength by performing the Leg Press from the same wide stance as their Deadlift. This isn’t usually possible since most Leg Press Platforms don’t have a wide platform.
However, narrow Quarter Leg Presses will help increase quad drive for Sumo Deadlifters.
Other Quad Dominate Deadlift Auxiliary Exercises
Back Quarter Squats
Front Quarter Squats
One Leg Step Ups holding Dumbbells