Not true. If the coil spring is the same length, then you're getting the lift from extending the effective length of the strut assembly. Now, you can do this by putting a spacer on top, or by moving the collar on the bottom up as in the case of the Bilstein, but in BOTH cases the way it all works is going to be the same and you're going to have the same range of motion.
The reason spacers are my preference is because they do not alter ride quality nearly as much from stock, they are far less expensive, and it's more predictable how much lift you're going to end up with.
I've got one truck in my driveway right now with 231,000 miles on it and it's had a 3" spacer lift on it for the last 15 years. And I just put a 1.5" spacer lift on the front of my new 2025 this past weekend actually. I'm very happy with both of them. I've done the Bilsteins in the past on other 4x4s but they ride stiff and I just don't like them.