The word "correct" is used often above. What does it mean? Were 5th grade students previously not taught to multiply fractions using the formula
a/b * c/d = (a*c)/(b*d) ?
Wu's point is that students are made to memorize an algorithm, rather than being taught why it works and how it fits into the bigger picture. He's right about that. EPGY may very well be different, but the vast majority of today's textbooks present algorithms with minimal or no explanation about the ideas behind them.
Regarding "correct," he means that a lot of teachers don't understand this stuff, either, and so they don't see how standard algorithms fit into the bigger picture of mathematics. This problem makes them susceptible to the flawed reasoning behind goofy algorithms like partial products and guess-and-check.
This stuff is the bigger picture of the problem with the Dolciani algebra textbooks blog post that you posted.
