Very true, and a big example of this happening are company shares being exchanged literally millions of times every trading day of stock markets worldwide.

Much of the key legal rights fall within having a majority of control. E.g. if you own 51% of a company then you would typically have a controlling share of it, opening possibilities of rights more significant to the remaining minority co-owners.

Ownership of any proportion all revolves around what the greatest power is both willing and capable of enforcing towards the particular property, asset, or "thing". Different kinds of "things" get different rules and these rules can change at any time.

The key point about ownership is enforcement of such arbitrary relationship between one legal entity and property or another legal entity.

Legal entity instead of "person" matters because ownership is largely not just between a person (or people) and property. For example a company is often recognised a legal body in its own right also capable of ownership of property, and a sovereign state is also able to own property.

I could claim ownership of, let's say your phone. However I could not enforce this ownership because there is a greater power arbitrating that you own your phone. That power being the ratified law of your land acknowledging the process in which you legally purchased your phone. If I stole your phone though, and no law enforcement was able to recover it, then your ownership bond is broken as I could now enforce my own ownership. On the flip side such an arbitrating power can equally enforce against your ownership of your phone, for example if it should decide your phone is to be seized as evidence in crime. So you only own your phone if appropriate enforcement continuously upholds your ownership of it.

We could think way beyond. Can we claim ownership of the planet Saturn? Of course, but neither of us, or realistically any arbitrating power, have any chance of enforcing that claim making it worthless.

That sounds more like AT&T being bad rather than VPN being good.

A VPN is just another link in the chain that could become a weak link. AT&T are likely inspecting your traffic to shape (prioritise) it as they see fit, for example if some chump is watching gigabyte after gigabyte of video that may be considered a lesser priority than say a messaging service. -- Your use of VPN would just impair AT&T's ability to accurately judge what your traffic is and classify it as "generic fluff".

That being said in the US didn't the FCC repeal net neutrality under the leadership of Ajit Pai, thus opening the doors for your ISPs to tier traffic into whatever fast and slow lanes they like? (E.g. cut deals with digital services to improve service quality, penalise those that refuse to pay more, etc.)