While strength is a significant factor, mental acknowledgement of what is necessary and when is still the real foundation. Shifting the foundation to reward poor technique as the better performance has definitely been a disservice to many clients. In most sports, performance is enhanced from improved strength/form/technique and to train something else hurts the performance in addition to the person so it's avoided more.
However, I think that learning to harden up helps a lot of people - until it doesn't. It's a tipping point for sure to walk someone up pain mountain. Once the benefits of learning to suffer are achieved, it's time to change the focus. I think really hard stuff is a great introduction, especially when the weights used and intensities reached are still considerably below biological thresholds of the individual. Tons of volume at a high intensity will likely hurt a new client but it won't injure them. As clients advance it becomes more likely to be injured due to the relativity of their limits. When strength is the foundation, there isn't a bad tipping point and it can't be "taken too far" or stop having positive benefits.