"Those green things are so obviously bile, that is why it is an IMPOSSIBILITY to flush clean"
I think it is possible to flush clean, at least for some people ... and at least on some flushes.
It is also possible to never get a single stone on any flush. There are people who never got a single stone out.
I think chemical reaction that takes place inside intestines ... one that results in bile precipitating into solid cholesterol (possibly a reaction between HCl and bile )... that reaction is not very stable and is definitively not one that you can safely bet on. It may happen ... or it may not.
There are people who flushed many times and never passed a single stone, but still passing bile.
There are people who stopped passing stones after several flushes ... then after some time .... flushes produced some stones again .. and again some flushes with no stones .. and again flushes with stones ... (Include me in this group ... I have had more then 3 flushes in a row with no stones or sometimes with very few stones 3 -4 very small stones ... .. I flushed more then 40 times so far ... 10 years).
There are people who get stones only on some of their flushes.