The article basically says that tackling problems in the music as soon as you make them is more important than spending more time practicing. This is very similar to the article I wrote about practicing called How Do I Raise My Standards. Those students who continue to make mistakes (instead of addressing them immediately) actually cause more trouble for themselves in the long run and it would be better, in some cases, for them to not practice at all.
The only thing I would add to what the article says is that it is possible to practice the music in a way that you minimize or even completely eliminate the mistakes. In my opinion, this is a best case scenario because musicians who never make mistakes while practicing have an entirely different outlook towards the music they are performing. They literally have no concept of failure. It can’t get any better than that.
One of the things you will learn in your private lessons with me is the techniques that lead to perfect practice, and thus, perfect performance. Yes, perfect practice is a rarity. I’m not saying that everyone who learns these techniques always plays everything perfectly. But shooting for that perfection puts us all in a far better starting place on each piece of music we learn. Combining these techniques with the immediate response to mistakes (as the linked article suggests) is a winning recipe for musical success.