The old checkbox indeed had the value 'obsolete' and the old code would convert the "obsolete" attribute value to PropertyPRUNE.

The new checkbox is named 'Prune' and the new code reads that value from the requests and adds it to the attributes. (I introduced SEARCH_ATTRIBUTE_SKIP == PropertyPRUNE == 'Prune' for consistency).

In other words: before this change we had 3 names for the same concept ('Prune', 'Skip' and 'obsolete'), and I (mostly) removed the 'obsolete' variation.