I have no issue with using pre-exhaust if you are skilled. But I do want to caution trainers to be very strong on your monitoring of clients when using this technique.
The incidence of injury when using pre-exhaustion is an issue. It is not wise to use with novice clients (training less than 2 years) and not very helpful for clients who do not have competitive goals. The risk to reward ratio is not good. While much of what I do with clients does take place in a fatigued state, I do not intentional try to fatigue a muscle or muscle group to put more stress on a target muscle/group. I can do this without using an exercise that would normally require assistance from other muscles to be performed safely and correctly.
I would recommend using variation and sound progression as opposed to this. In any case, get educated on any type of training you want to use before attempting the new technique. Be safe.