The SampleResult class keeps a copy of the relevant sample save configuration. This is needed in order to store the appropriate sample entries. It needs to be kept with the result until that is saved, but probably does not need to be saved with the result fields. This would save a lot of space in XML format files.
Note: this only applies to the StatisticalSampleResult class, which currently does not have a converter. Cannot re-use the SampleResult converter as is, because that cannot unmarshall the previous format.
This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/2687