HFsets should only be used to chase, I had very little success in using their carbon taps to even thread an exhaust stud I broke and center drilled out. the threads were cut so loose that I had to enlarge to a metric and stud it to save it.
I don't doubt that a bit. I would never even waste my money buying a cheap set of Chinese taps. I generally buy the best I can get, even if it means waiting a while until I have the money for them.