embedded is intended for a pure-Java SE environment. This means no Java EE specific packaging is allowed: EAR, WAR, RAR, SAR, etc...
Only jars (no nested jars)
The reason for this is that in the embedded environment you have no control over classloading and get everything from the classpath. An EAR has nested jars, these jars would need to be added to the classpath. This is impossible in SE.