It's been a long time since I've been in the industry, but using
bacteria to break down oils is a common method of dealing with them, to
the extent that many large trucking companies with large service bays
often have oil treatment facilities that use the bacteria to break down
the oil to something "Less toxic".
It is possible that these bacteria are airborne and could find their way
into your tank. It is also possible that the slow release is just not
noticeable; especially assuming you do water changes.