This is my point. When ALL teams move to complete transfers then it is better. Deals get done, cause most are procrastinators. I think there will be plenty of movement, but mainly in Europe. A few EPL players will also leave, most probably.
Let's take Sporting as an example. Currently nobody we know about wants to buy Bruno. If our window closes and we submit a final day offer, Sporting might think that another team might offer more later in their window. They will be under no pressure to sell. Whereas, if it was the last day for everyone then they just might go for it.