Except that the paper did not compare different training methods. The used the same method since it has been long established that training to failure anywhere in the 5-30 reps (perhaps even more, the upper limit has not been established yet) gets the same results from the hypertrophy point of view.

So basically the study's results are "there are individual differences in how people respond to training". Wow, such news, so research, much insight. /s

Therefore study itself is dumb and the misleading title makes it even worse.