What people are talking about there is that when I send you a message, it leaves my device encrypted, and can only be decrypted by you, on your device. Whatever servers it goes through, in order to get to you, cannot decrypt it at all. Law enforcement, third-party companies, doesn't matter, they can't see it, only you and I can.

At least in the states they faced legal penalties for such a claim (albeit a slap on the wrist).

My understanding is, to be E2E encrypted, the keys must only be known by you and the actual other user you're communicating with. With https, this is not the case: you're only communicating with the server, which then relays the messages. However, the server can see everything.

You can use the term in different contexts, depending on what you consider the "ends": If you think of your machine as one end and the server as the other, it is technically E2E encrypted.

But in the more meaningful sense where your device is one end and your communication partner's device is the other end, it is not.

But the owner of the domain can decide at which point they terminate.

Could be that your connection is just encrypted until a proxy that's inbetween.