In every large org, including disney, there are people who will fuck with you to the full extent of the terms and laws if they think it can increase profit... they do not care about quality, experience, or morals. I've fought these people about marketing emails at dozens of orgs as a consultant.
I guarantee they will eventually use this to show more ads. The goldfish grows to fit its bowl.
They don't stop at terms and laws. They stop at what loses money, through customer churn or lawsuits.
Typically the only restraining force is a founder who cares.
That's why I don't really care that much about terms and conditions. Just because they say they can doesn't mean that they will, conversely, the writing can be misleading to anyone who isn't a specialized lawyer, so most people can't really tell what the terms and condition let them do anyways.
I usually go for reputation and precedent rather then legalese. And in the case of Disney, they had ads in their video tapes and DVDs, so I don't need to read the user agreement to know that it has a good chance to come to Disney+, whatever the legal pathway is.