The values from properties in a PropertiesStep in SoapUI are also saved to the project XML ?

It seems that dynamic generated proeprties, which are saved in a PropertiesStep with a Groovy script like:

testRunner.testCase.testSteps["DynamicProperties"].setPropertyValue("MyId", "abc")

Are persisted in the XML project file:

<con:testStep type="properties" name="DynamicProperties" id="d211dd62-4875-4b60-bde8-cb542fa7df47">
<con:settings/>
<con:config xsi:type="con:PropertiesStep" saveFirst="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <con:properties>
	<con:property>
	  <con:name>MyId</con:name>
	  <con:value>abc</con:value>
	</con:property>
  </con:properties>
</con:config>
</con:testStep>

Which is not what I want, because when this value is dynamic (like a timestamp), the XML project file is updated each time I run a test ?