I don’t remember any other instance in the Catholic Church when input from laity on that kind of scale had been sought.
Sure, they do get lay experts in different fields to give advice. But I can’t think of any cases when regular churchgoers were asked for their opinion. Ecumenical Councils and Synods, as far as I know, have always sought advice from the local Bishops about what the agenda should be, and in theory they would be in touch with what the people from their local Churches would say and they could convey that for them. But that seems to be as far as it has ever gone, all the way back to the Council of Jerusalem.
Can anyone back this up or correct me? The historicity of this all is fascinating.