[SOLVED] Keep all parameter of Generate Attributes operator with attribute overw

Isn't keep_all meant to specify whether or not to keep those attributes that are not generated within the Generate Attributes operator?

However, the following process (for example) produces an empty exampleset where I would have expected attribute a to survive.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="5.3.000">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="5.3.000" expanded="true" name="Process">
    <process expanded="true" height="654" width="980">
      <operator activated="true" class="generate_data_user_specification" compatibility="5.3.000" expanded="true" height="60" name="Generate Data by User Specification" width="90" x="112" y="75">
        <list key="attribute_values">
          <parameter key="a" value="1"/>
          <parameter key="b" value="2"/>
        </list>
        <list key="set_additional_roles"/>
      </operator>
      <operator activated="true" class="generate_attributes" compatibility="5.3.000" expanded="true" height="76" name="Generate Attributes" width="90" x="313" y="75">
        <list key="function_descriptions">
          <parameter key="a" value="a"/>
        </list>
        <parameter key="keep_all" value="false"/>
      </operator>
      <connect from_op="Generate Data by User Specification" from_port="output" to_op="Generate Attributes" to_port="example set input"/>
      <connect from_op="Generate Attributes" from_port="example set output" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

Is this the intended behavior?