Pretty much all these sites can view every bit of content you submit to them for moderation purposes. Many of them state your data can teach learning models.
If you really want it private, you don't want it on the cloud/social media sites.
A general rule is people don't know shit when it comes to legal definitions. When you have a video it's private to you. When you give that video to a friend it's 'private' between both of you. And when you put a private video on youtube it's 'private' between you and the conglomerate entity of hundreds of thousands of people and all their contractors called Google.
Now the contractor did break the rule and shared it, but your idea of private as no one will see it is the broken expectation.
>regardless of privacy
Maybe you should read the TOS before you use services, you don't have any of that.
If it isn't end-to-end encrypted, then the platform operator has access.