+1 for removing the Jetty Maven plugin and using Cargo (see just a few lines above this section of the POM file).

As for the property, you're right that many of our properties are used only once (in the pluginManagement section). But having all the version specified in the properties makes it a lot easier to quickly see which properties and which plugins we're actually using. Plus, if we need/want to upgrade any of the versions, we know the one section of the parent POM to modify.