NASA is elevating its digital platforms for the benefit of all by revamping its flagship and science websites, adding its first on-demand streaming service, and upgrading the NASA app. With these changes, everyone will have access to a new world of content from the space agency.
Sure, why not. That’s all it means in the context of Disney+.
From their generic FAQ:
from my limited perspective, the word “plus” is to indicate the rest studios/companies that are included in the Disney (parent) company