This is another one of those little technical debates we all like to have. Most of it comes down to the intent of what it we're trying to achieve and how we place language around it.

If I want to stream something, it traditionally means I want to watch it in (near) real time as it is being downloaded, without necessarily having to store the entire thing. If I am downloading, I want the whole thing first before I watch it and I want to keep all of it.

Depending on the intent, will depend on the technical solution put in place to do that thing well, as there are technical differences. So yes, to watch a movie it requires downloading it in some way shape or form.

Something that doesn't need as much discussion as it gets. One of those "well technically it is..." type of arguments.