The movie has an unobtrusive crawl around the 23 minute mark:
"Decided to pirate our movie, eh? Now you'll have to deal with these scroll-y bits. If you like what you see, buy the drm-free version at www.storyofmojang.com so that we can afford to keep making movies. Thanks!"
Why not? The producers shared that stuff on TPB because it'd end up there eventually, and because they understand that there are reasons for kind-of-sort-of-ethically-fine 'pirating'.
You grabbed the movie. You didn't got the payed version (otherwise you wouldn't complain) and got a reference to pirating. Because .. you pirated the movie.
They uploaded it to be in control on TPB. They explicitly ask for you to go ahead, check it and please support them by buying the movie. If you don't do that, you're pirating the movie with the help of the producers. At least in my world.
(Downloading it right now, net's slow. Will watch it with my wife and invest the USD 8 if it has a couple decent / funny / interesting scenes)
"Piracy" refers not to free downloads, but to copyright infringement. Do I "pirate" a Wikipedia article every time I visit the site? Do I "pirate" Ubuntu when I download an ISO?
You could not be less correct when you claim that downloading this torrent from the content creators is an act of piracy. This demonstrates a fundamentally perverse view of both the laws and ethics of intellectual property on the part of you and these content creators.
The moment the producer places the movie on pirate bay themselves and encourages you to download it, then it is no longer piracy, it is using torrents as a legitimate, distributed downloading service, like it was made to be.
If anything, they uploaded a shareware version of the movie to the pirate bay. Them saying you're pirating it is inaccurate. Instead it should be something like "Hey! I see you torrented our movie! Thanks for watching it; and if you feel like, please download the pay-for version of this movie to support us! (We'll even remove this ask for money from the official!)"
Piracy is, in the lazy short verison, acquiring without permission. Torrenting != Piracy when you have permission. e.g. every World of Warcraft update.