Quoting from the article at the above mentioned URL
"Using markup languages to generate user interfaces proves advantageous due to those languages' ubiquity and light weight. However, a markup-language-based UI is fairly limited. Java Web Start overcomes this main limitation while preserving some of a markup-language UI's main benefits, such as using a network URL as a launching point, updating client applications without intervention, and so on. "
How does JWS help with "updating client applications without intervention" ?
Each time a JWS app is launched on the client, JWS checks whether there's a new version available on the server. If there is, it offers to update the version installed on the client (or possibly even does that automatically, I don't recall the details). There's nothing the developer or the user need to do about it, hence "no intervention".