Hamstring stretch with a guided path.
Hinge from the hips with a flat back, the knees barely move.
The Smith machine turns the RDL into a pure hinge drill, the bar's fixed track keeps the load in one clean vertical line while you push your hips back and feed the hamstrings into a deep stretch. The glutes finish each rep by driving the hips forward to tall. Because the machine handles the bar path, all your attention goes to the two things that make an RDL work, the hip hinge and the stretch.
For hamstring stimulus, yes. The stretch and hip hinge are identical, the machine just removes the balance and bar-path management. Purists will point out the lost stabiliser work, but for hypertrophy the fixed track is a feature, not a flaw.
To the point of a strong hamstring stretch with a flat back, typically around mid shin. Depth is set by your hamstrings, not the floor, going lower with a rounding back is losing the exercise, not winning it.
You are drifting away from the bar or bending your knees into a squat. Keep the bar brushing your thighs the whole way down, push the hips straight back, and keep the knee bend slight and fixed from the first rep to the last.
