Maven updates its plugin metadata then says it can't find the plugin - WTF?

Trying to generate the IntelliJ project files for a Maven 2 project.
Then I got an error:

mvn idea:idea
[INFO] Scanning for projects...
[INFO] Searching repository for plugin with prefix: 'idea'.
[INFO] artifact org.apache.maven.plugins:maven-idea-plugin: checking
for updates from central
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Error building POM (may not be this project's POM).

Project ID: org.apache.maven.plugins:maven-idea-plugin

Reason: Error getting POM for
'org.apache.maven.plugins:maven-idea-plugin' from the repository:
Failed to resolve artifact, possibly due to a repository list that is
not appropriately equipped for this artifact's metadata.
org.apache.maven.plugins:maven-idea-plugin:pom:2.2-SNAPSHOT

from the specified remote repositories:
central (http://repo1.maven.org/maven2)

Now I look in my Maven repository, in the maven-idea-plugin directory, in

\.m2\repository\org\apache\maven\plugins\maven-idea-plugin

and I find the maven-metadata-central.xml which has this:

<?xml version="1.0"?><metadata>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-idea-plugin</artifactId>
<versioning>
<latest>2.2-SNAPSHOT</latest>
<release>2.1</release>
<versions>
<version>2.0-beta-1</version>
<version>2.0</version>
<version>2.1</version>
<version>2.0-beta-2-SNAPSHOT</version>
<version>2.0-SNAPSHOT</version>
<version>2.1-SNAPSHOT</version>
<version>2.2-SNAPSHOT</version>
</versions>
<lastUpdated>20070716221242</lastUpdated>
</versioning>
</metadata>

But when I look in the location:

http://repo1.maven.org/maven2/org/apache/maven/plugins/maven-idea-plugin/

And get the maven-metadata.xml, it has:

<metadata>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-idea-plugin</artifactId>

<versioning>
<latest>2.1</latest>
<release>2.1</release>

<versions>
<version>2.0-beta-1</version>
<version>2.0</version>
<version>2.1</version>
</versions>

<lastUpdated>20070604220104</lastUpdated>

</versioning>

</metadata>

The only possible reason I can think of for this happening is that
Maven is getting the metadata from somewhere else. We are using
Artifactory and one of the repositories we have set up is an entry
pointing to http://people.apache.org/repo/m2-incubating-repository.
The artifactory.config.xml contains this:

<remoteRepository>
<key>apache-m2-incubating</key>
<handleReleases>true</handleReleases>
<handleSnapshots>true</handleSnapshots>
<excludesPattern>org/artifactory/**,org/jfrog/**,au/com/company/**</excludesPattern>
<url>http://people.apache.org/repo/m2-incubating-repository
<proxyRef>work-proxy</proxyRef>
</remoteRepository>

Now in this repository, there is a directory for maven-idea plugin, at

http://people.apache.org/repo/m2-snapshot-repository/org/apache/maven/plugins/maven-idea-plugin/

and there is a file
http://people.apache.org/repo/m2-snapshot-repository/org/apache/maven/plugins/maven-idea-plugin/maven-metadata.xml
that contains:

−
<metadata>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-idea-plugin</artifactId>
<version>2.0-beta-2-SNAPSHOT</version>
<versioning>
<latest>2.2-SNAPSHOT</latest>
<versions>
<version>2.0-beta-2-SNAPSHOT</version>
<version>2.0-SNAPSHOT</version>
<version>2.1-SNAPSHOT</version>
<version>2.2-SNAPSHOT</version>
</versions>
<lastUpdated>20070716221242</lastUpdated>
</versioning>
</metadata>

Now the strange thing is that this info is not exactly the same as
what's in my local repository. So it looks like the
maven-metadata-central.xml I have for maven-idea-plugin did *not* come
from this location. So where did it come from? I should probably add
to the exclusion list for the above repository so it doesn't try and
get maven plugins from there. But from the error message I got, it
looks like it only goes to the central repository at repo1.maven.org
for plugin updates. If that's the case, why does it seem to go
somewhere else for it's plugin updates?

What the hell is Maven actually doing?