I suspect when Frank Lloyd Wright was speaking of "windows", he meant the cultural idea of a window, but off course spaces are open and have openings connecting to the horizon / landscape, to Franks defense! haha
a "window" can sometimes be a hole in the wall, which I think Frank Lloyd wright had a problem with, a properly placed "opening" is essential off course. I had to watch video again, I think Siza and Wright might be saying the same thing in a different way. Siza one of my favorite architects btw
As time ticks on, I find my self wondering about the thoughts and processes architects have when designing a project. This was a great interview to watch and well made to the film maker.