The problem with back extensions on the calf machine like in your vid is that the range of motion is cut short. You’d be better off swapping out a different lower back exercise like good mornings. One alternative I like is holding the top position of a back extension for time, not reps, to work lower back strength-endurance. So that could be an option too.
For GHRs though, it’s not uncommon for people to use the knee pads at the pulldown station the same way you’re using the calf machine. So that should be fine.