If the runtime name of a dynamic VDB (*-vdb.xml) does not contain ".xml" extension, then it is undeployable [3]. If the runtime name does not contain ".xml", EAP tries to load it as zip [2].
Management api commands [1]. I suggest to add at least note to the documentation.

[1]

• fail: /deployment=myvdb:add(runtime-name=myvdbrn,enabled=true,content=[{archive=false,path=/path/to/my-vdb.xml}])
• fail: deploy /path/to/my-vdb.xml --name=myvdb --runtime-name=myvdbrn
• ok: /deployment=myvdb:add(runtime-name=myvdbrn,enabled=false,content=[{archive=false,path=/path/to/my-vdb.xml}])
  fail: /deployment=myvdb:deploy

[2]
org.jboss.as:jboss-as-server:7.5.0.Final-redhat-21
org.jboss.as.server.deployment.module.DeploymentRootMountProcessor#deploy(DeploymentPhaseContext)

if(mountExploded) {
type = MountType.EXPANDED;
} else if (deploymentName.endsWith(".xml")) {
type = MountType.REAL;
} else {
type = MountType.ZIP;
}

[3]
ERROR [org.jboss.msc.service.fail] (MSC service thread 1-6) MSC000001: Failed to start service jboss.deployment.unit.newvdbxmlrn.STRUCTURE: org.jboss.msc.service.StartException in service jboss.deployment.unit.newvdbxmlrn.STRUCTURE: JBAS018733: Failed to process phase STRUCTURE of deployment "newvdbxmlrn"
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:166) [jboss-as-server-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.startService(ServiceControllerImpl.java:1980) [jboss-msc-1.1.5.Final-redhat-1.jar:1.1.5.Final-redhat-1]
at org.jboss.msc.service.ServiceControllerImpl$StartTask.run(ServiceControllerImpl.java:1913) [jboss-msc-1.1.5.Final-redhat-1.jar:1.1.5.Final-redhat-1]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [rt.jar:1.8.0_40]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [rt.jar:1.8.0_40]
at java.lang.Thread.run(Thread.java:745) [rt.jar:1.8.0_40]
Caused by: org.jboss.as.server.deployment.DeploymentUnitProcessingException: JBAS018740: Failed to mount deployment content
at org.jboss.as.server.deployment.module.DeploymentRootMountProcessor.deploy(DeploymentRootMountProcessor.java:97) [jboss-as-server-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
at org.jboss.as.server.deployment.DeploymentUnitPhaseService.start(DeploymentUnitPhaseService.java:159) [jboss-as-server-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
... 5 more
Caused by: java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method) [rt.jar:1.8.0_40]
at java.util.zip.ZipFile.<init>(ZipFile.java:220) [rt.jar:1.8.0_40]
at java.util.zip.ZipFile.<init>(ZipFile.java:150) [rt.jar:1.8.0_40]
at java.util.jar.JarFile.<init>(JarFile.java:166) [rt.jar:1.8.0_40]
at java.util.jar.JarFile.<init>(JarFile.java:130) [rt.jar:1.8.0_40]
at org.jboss.vfs.spi.JavaZipFileSystem.<init>(JavaZipFileSystem.java:90) [jboss-vfs-3.2.9.Final-redhat-1.jar:3.2.9.Final-redhat-1]
at org.jboss.vfs.spi.JavaZipFileSystem.<init>(JavaZipFileSystem.java:77) [jboss-vfs-3.2.9.Final-redhat-1.jar:3.2.9.Final-redhat-1]
at org.jboss.vfs.VFS.mountZip(VFS.java:386) [jboss-vfs-3.2.9.Final-redhat-1.jar:3.2.9.Final-redhat-1]
at org.jboss.vfs.VFS.mountZip(VFS.java:410) [jboss-vfs-3.2.9.Final-redhat-1.jar:3.2.9.Final-redhat-1]
at org.jboss.as.server.deployment.DeploymentMountProvider$Factory$ServerDeploymentRepositoryImpl.mountDeploymentContent(DeploymentMountProvider.java:105) [jboss-as-server-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
at org.jboss.as.server.deployment.module.DeploymentRootMountProcessor.deploy(DeploymentRootMountProcessor.java:93) [jboss-as-server-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
... 6 more