Multiple connections feature is controlled by system property 'jbpm.enable.multi.con', Looking at the source code (e.g. [1] and [2]), this property is being questioned only for existence, not for actual value: 

System.getProperty("jbpm.enable.multi.con") == null

=> multiple connections feature is switched on if the property is defined no matter what value it has, even if the value is "false", which is a non-standard behaviour.

expected behaviour:
jbpm.enable.multi.con=false => multiple connections disabled
jbpm.enable.multi.con=true => multiple connections enabled
jbpm.enable.multi.con undefined => default behaviour - mult. conn. disabled

Version-Release number of selected component (if applicable):
BPMS 6.0.0.ER2

[1] https://github.com/droolsjbpm/jbpm/blob/master/jbpm-flow/src/main/java/org/jbpm/workflow/core/node/ActionNode.java
[2] https://github.com/droolsjbpm/jbpm/blob/master/jbpm-flow/src/main/java/org/jbpm/workflow/core/node/EndNode.java