Example XML use the old style XSD -- "21.11.4. Custom Cache Store Configuration (Library Mode)"

CustomerCacheStore example use the outdated XML format to add a property.

Current (XSD 6.x) documented:
<store class="org.infinispan.custom.CustomCacheStore" preload="true" shared="true">
<properties>
<property name="customStoreProperty" value="10" />
</properties>
</store>

Correct is
<store class="org.infinispan.custom.CustomCacheStore" preload="true" shared="true">
<property name="customStoreProperty">10</property>
</store>