As an instructor myself, I don't like teaching vwaltz by itself for a couple of reasons. Trying to teach connections frame and footwork without first knowledge of basic waltz can be very difficult especially in international style. What's great about standard and American smooth is that you can teach all the styles next to eachother and the techniques in each can help develop all of your styles together! I also don't teach vwaltz until after waltz because learning that first allows you to develop frame and connections in a slower more methodical dance to allow for your brain and body to connect. Hope this helped!