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It’s helpful when trying for new 1RMs.
Edit: I know I didn’t actually answer your question. The body is fooled into thinking that the hard set is easier than it really is. It’s a psychological trick that works in some cases.
Another rep scheme that I’ve done that works on a similar principle is 642246 where the first 3 sets are hard and the second 3 sets are slightly heavier than the respective weight of the previous 3 sets. Your body thinks they are the same so it just does it. The next workout the weights from the second 3 sets become the weight for the first 3 sets.