No, it does not mean so..
If you use the expresion assignment(<from xsi:type="tFormalExpression">#{transportMap}</from>), it is resolved as an string, but if you map your process variable like this
<sourceRef>transportMap</sourceRef>
<targetRef>_12_ContentInput</targetRef>
I think should work.
You can check for example here:
https://github.com/Salaboy/emergency-service-drools-app/blob/master/emergency-service-core/src/main/resources/processes/procedures/DefaultHeartAttackProcedure.bpmn
To see how that parameters to the user task are sent.
For example,
<dataInputAssociation>
<sourceRef>emergency</sourceRef>
<targetRef>_6_emergencyInput</targetRef>
</dataInputAssociation>
Demian