The problem with doing this is if you hardcoded a launch video option, and the video was taken offline (as Netflix changes their watch now library quite often) then your direct link would no longer work to the desired effect.
You can code it to launch the channel as you are doing, which is probably the best way long-term. If you research the built-in search for Roku, you notice their lists are not 100% current/accurate - ie
Search for "South Park" - you get the seasons, and you get the movie.
The Movie says it's only available on Netflix, however, if you go to Amazon video on demand separately on roku, you can watch it there too but the Roku home page search doesn't indicate anything else for that selection.