Ah yeah sorry, for me somehow php is not needed inside occ command, was wondering myself 
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Okay, so cache cleanup seems not to be the related background job. I hope to soon get some answer here about other daily background jobs of Nextcloud. Will reply if I have some idea/other jobs to test. Maybe in between someone with more insight can help you further.
Also consider to open a issue on github (bug tracker), as you are closer to the developers with more detailed knowledge there: Issues · nextcloud/server · GitHub