I don't think that this is a dupe: It really downloads the artifacts sometimes not just the poms. We are using the plain SNAPSHOT version. Now perhaps the interesting part is that this happens during a build where these artifacts have just been created and put in the local repository. So a simplified example is, you have two modules A and B, both have the version as SNAPSHOT and B depends on A. Now you build both modules at once, first A gets build and is installed in the local repo, then B gets build, downloads a snapshot of A from the remote server, builds and then uses the local version of B. I'm not exactly sure of this last part, but upto now, everytime changes locally done to A where available in B although B downloaded a SNAPSHOT of A which could not have these local changes.
This does not happen always, but from time to time.