It does not necessarily have to be bitcoin blockchain, that is the approach towards achieving web 3.0, in which blockchain will be used to store data like vidoes or any of such, rather than relying on centralized organizations.
If you are talking about projects like Storj, I don't think that the data is stored on the blockchain (although I don't know how it works).
I'd expect the blockchain only records transactions, like adding and removing files from the distributed cloud.
The blockchain, if done properly, doesn't allow past data to be changed. And that may not suitable for files. And that's expensive to store. Movies don't need
all nodes store them.