Getting arbitrary depth=2 dependencies when using optional=true

When using a dependency section like this in a WAR (just an excerpt - these are not the culprit to my knowledge):
<dependency>
<groupId>xmlbeans</groupId>
<artifactId>xbean</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>xmlbeans</groupId>
<artifactId>xbean_xpath</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>xml-apis</groupId>
<artifactId>xml-apis</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>xml-resolver</groupId>
<artifactId>xml-resolver</artifactId>
<optional>true</optional>
</dependency>

I am getting artifacts with a depth of 2 - when nothing should resolve. Only depth 1 (non-optional deps, plus their deps, etc) should be resolving. i.e.

[INFO] mq: 2
[INFO] mqjms: 2
[INFO] spring-orm: 2
[INFO] struts: 1
[INFO] child: commons-beanutils:commons-beanutils:jar:1.6.1:compile (2; disabled)
[INFO] child: commons-collections:commons-collections:jar:3.1:compile (2; disabled)
[INFO] child: struts:struts-legacy:jar:1.1:compile (2; enabled)
[INFO] child: commons-digester:commons-digester:jar:1.6:compile (2; disabled)
[INFO] child: commons-fileupload:commons-fileupload:jar:1.0:compile (2; enabled)
[INFO] child: commons-lang:commons-lang:jar:2.1:compile (2; disabled)
[INFO] child: commons-logging:commons-logging:jar:1.0:compile (2; disabled)
[INFO] child: commons-validator:commons-validator:jar:1.1.4:compile (2; disabled)
[INFO] child: oro:oro:jar:2.0.7:compile (2; disabled)
[INFO] child: javax.sql:jdbc-stdext:jar:2.0:compile (2; enabled)
[INFO] commons-logging: 1
[INFO] child: log4j:log4j:jar:1.2.6:compile (2; enabled)
[INFO] child: logkit:logkit:jar:1.0.1:compile (2; enabled)
[INFO] child: avalon-framework:avalon-framework:jar:4.1.3:compile (2; enabled)
[INFO] distribution-service-client-jar: 2
[INFO] jdbc-stdext: 2
[INFO] struts-bean: 1
[INFO] cmf-nol-submit-jar: 2
[INFO] mqiiop: 2
[INFO] distribution-service-ejb: 2
[INFO] jaxen: 2
[INFO] spring-dao: 2
[INFO] struts-tiles: 1
[INFO] cmf-final-jar: 2
[INFO] struts-legacy: 2
[INFO] standard: 1
[INFO] saxpath: 2
[INFO] jstl: 1
[INFO] nw-exception: 1
[INFO] relaxngDatatype: 2
[INFO] mqbind: 2
[INFO] struts-logic: 1
[INFO] commons-fileupload: 2
[INFO] isorelax: 2
[INFO] spring-core: 2
[INFO] log4j: 1
[INFO] msv: 2
[INFO] struts-nested: 1
[INFO] nw-struts: 1
[INFO] child: struts:struts:jar:1.1:compile (2; disabled)
[INFO] struts-html: 1
[INFO] authorization-tag-jar: 1
[INFO] child: commons-logging:commons-logging:jar:1.0.4:compile (2; disabled)
[INFO] child: log4j:log4j:jar:1.2.7:compile (2; disabled)
[INFO] child: com.nationwide.common:nw-exception:jar:1.2.0:compile (2; disabled)
[INFO] child: com.nationwide.pc.claims.horizon:simple-security-client-jar:jar:2.0.0:compile (2; disabled)