The Mythical Man-Month, published a year before Wirth's book, provides the most well-known quote on the subject (though he uses now antiquated language):

"Show me your flowchart and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won't usually need your flowchart; it'll be obvious."

But I don't think Brooks was trying to suggest it was an original idea to him or his team, either. I imagine there were a decent number of people who reached the same conclusion independently.