FilterSimilarPages key ... not working?

When I specify:

<key>FilterSimilarPages</key>
<false/>

in one of my own plugins, it does not seem to take effect i.e., when I check the Settings tab of the returned results, I find the Similar Pages filter to be checked (true). When I uncheck it and start the query again, I get more results so clearly the filter is indeed turned off.

Did I specify the proper key in the plist or is this not working as I understand it?

(DAP 3.10)

The option of search sets en-/disables filtering of similar pages for all plugins used by the search set whereas the FilterSimilarPages key specifies whether a plugin supports filtering of similar pages. Could you send a copy of the plugin to cgrunenberg - at - devon-technologies.com? Thanks in advance!