I have both Animate CC and Flash CC 2015 installed on my machine.
I created a copy of an FLA and opened one in Animate and one in Flash, then exported both. Upon examination of the JS output, the symbols in the Flash output were comprised of Containers and MovieClips, this is exactly what I expected. However, when I looked at the Animate output, all symbols, regardless of the length of the timeline, were comprised of MovieClips - even those that are Containers in the Flash output.
Does anyone know why this is the case? It's not a huge issue, I can deal with either output, I'm just interested as to why there is a difference.
The version of CreateJS has changed over time, and that team may have rethought how to do things.