I setup a very simple experiment, so simple you could laugh but at least it reaches a conclusion. Since most here are saying flourite hasn't changed their water and that I found only a tiny handful of testimonies that fluorite can lower GH and KH, I had to prove it to myself.
With two 20 gallon aquariums, and 2 AC150 filter on each (both with 1 brand new sponge) I put into one tank just plain tap water, and into the other, tap water and brand new flourite. I tested the tap before filling the tanks and after, and confirmed that the parameters where the same during the entire filling process. Even tested both tanks right after filling, and expectedly they had the same parameters.
So then, I let the filters run them for two days and tested them tonight. Here are the parameters:
Tank with Tap Water
Tank with Tap Water and Flourite
Well there you have it. In rare occasions Flourite will change your water parameters.
What set my case apart for most is that my water is very hard. Carbonates (KH) are not very soluble, and with my high levels to begin with, all I can assume is something in the fluorite percipitated/bonded them out of solution. The Ca++ and Mg++ could have been collected at the CEC spots in fluorite, thus lowering GH.