To reproduce, replace ace:dataTable content in dataExporterExcludeFromExport.xhtml file:

<ace:dataTable id="carData"
                                  value="#{excludeFromExport.cars}"
                                  var="car"
                                  rows="15">
               <ace:column headerText="Name">
                    <h:outputText value="#{car.name}"/>
                </ace:column>
                
                <ace:column headerText="Chassis / Weight">
                    <h:outputText value="#{car.chassis} / ">
                        <ace:excludeFromExport rendered="true"/>
                    </h:outputText>
                    <h:outputText value="#{car.weight}lbs.">
                        <ace:excludeFromExport rendered="false"/>
                    </h:outputText>
                </ace:column>
                
                <ace:column headerText="Accel / MPG">
                    <h:outputText value="#{car.acceleration} / ">
                        <ace:excludeFromExport rendered="false"/>
                    </h:outputText>
                    <h:outputText value="#{car.mpg}">
                        <ace:excludeFromExport rendered="false"/>
                    </h:outputText>
                </ace:column>
                
                <ace:column headerText="Cost">
                    <ice:outputText value="#{car.cost}">
                        <f:convertNumber type="currency"
                                         currencySymbol="$"
                                         groupingUsed="true"
                                         minFractionDigits="2"
                                         maxFractionDigits="2"/>
                        <ace:excludeFromExport rendered="false"/>
                    </ice:outputText>
                </ace:column>
            </ace:dataTable>

PLEASE NOTE: Only the name column will be exported to a file of given type.
Rendered attribute value (either static or dynamic via EL expression) is not taken into consideration while inside of the ace:excludeFromExport component.