Biblatex Cleanup for moving year+ month to Date field not working

[Siedlerchr]

Version 3.7, I think it dit not work in 3.6, too.
According to the code, the Biblatex Cleanup should cleanup/move the fields year + months etc to date

However, it currently gives always "No Entry needed a cleanup".
'Tested with different entrytypes and both year and month were set.

@Article{Orlowski;2011,
  author        = {Adam Czarnecki; Cezary Orłowski;},
  title         = {Application of Ontology In the ITIL Domain},
  year          = {2011},
  month         = jan,
}

https://github.com/JabRef/jabref/blob/master/src/main/java/net/sf/jabref/logic/cleanup/BiblatexCleanup.java