I don’t understand the different levels of it. Can you explain?
It depends on how deeply involved with the cult a non-baptized person is, coupled with how dependent they are on baptized family members. For example, let's say someone is born into the cult. They start off by tagging along in door-to-door preaching and giving comments at the meetings. In their early years they repeat very short, simple comments given to them by their parents. As they get older, they are able to formulate their own comments that are more complex than a one or two word answer. This also applies to preaching. They soon transition from being the shy little kid offering grownups the Watchtower and Awake magazines, to being confident enough to hold their own with the people that answer the door.
This leads to the next step which is becoming an unbaptized publisher, meaning that they are responsible for reporting their preaching activity each month. This is also the first time that they have to formally meet with the elders in order to be "approved" if they even "qualify" for this "privilege". Meeting with the elders at a young age conditions you to see them as the ultimate authority figures in your life. You're only good enough if they say you are good enough.
The next step is to become active in going up in front of the congregation and carrying out different assignments. If you are male, then you either read from the Bible, prepare a short Bible discourse, or you reenact preaching scenarios with a male partner. If you are female, then you partner with another female and you also reenact preaching scenarios. This is another step that requires approval from the elders.
When someone has made it to this point while growing up in the organization, they are basically viewed as a baptized member. They might even hear some people say, "I thought you were already baptized!" I used to get that sometimes. So now the pressure is on. This is the only world you know, so it's not like you chose it or something. You might not even feel like there's anything special about it. You were just doing what you've always been doing since you popped into the world. You know what everyone expects of you, and you don't want to let anyone down. At this point some people yield to the pressure, and some people don't.
If you don't yield to the pressure and decide to go your own way, you were already so deeply involved with everything that some people thought you were a full-fledged member. This is how you can be shunned without ever having to be baptized, and it's made even worse for those who are dependent on JW parents or relatives. Depending on how you show that you no longer wish to be a part of the organization, the elders might even make an announcement "warning" the congregation about you. They'll say, "_______________ _______________ is no longer an approved associate," or something to that effect. I've seen it happen.
Now contrast that with a celebrity athlete, who probably (as far as I know) never:
1. was regular in preaching
2. commented regularly
3. met with elders
4. became an unbaptized publisher
5. did congregation assignments
Serena and Venus most likely went to a few meetings growing up, and they probably went to every memorial. That's probably as far as it went. I would imagine that they spent most of their time on tennis, and as successful as they are, they aren't dependent on anyone for financial support. People probably depend on them, including family. They aren't under the jurisdiction of any particular congregation, and they have the freedom of wealth. They keep talking about the organization for whatever reason, but simply put, they are just normal non-cult members, and they can do whatever they want without any backlash from anyone.