At the risk of nit-picking, I think there were two different recommendations made at different points in time by Dr. Darden regarding 30-10-30.
He originally introduced the method in the Killing Fat book. I don’t have that book, so I don’t know how much detail he provided about protocol execution. However, in June of 2019, he published an article here which described a study he did with three teenagers, called Growth Explosion: The 30-10-30 Technique (link below).
In that 2019 study, 30-10-30 was only used once per week, and it was suggested that you might not be able to get the full 10 reps in the middle, or control the descent well enough to hit 30 seconds on the final negative, and that was OK. That certainly implies training to failure.
In the more recent ebook, he now recommends training with 30-10-30 three times a week. What made the increased frequency possible? Staying away from failure. That isn’t my words or conclusions. That is Dr. Darden’s own words, as found in a update that was added to the 2019 article:
BREAKING NEW PROGRAM UPDATE
…
I’ve also found that NOT going to failure with this method actually produces the best gains and allows trainees to work out three times a week.”
So there clearly was a shift in focus away from training to failure, as an explicitly recommendation by Dr. Darden. That is what some people are reacting to….