Anthony A, rather than just rehashing all the unpleasantness from the other thread (which I'm not saying was all from your side, BTW), there were some salient points inserted between all the "mine's bigger than yours" nonsense. These were posted by TH0001 and someone linked DaveKG--that there are lubricants and oils in these polishes, which need to stay between the pad and the paint of a rotary spinning at 1500 RPM...and depending on conditions these may or may not be left on the paint, be difficult to remove, and/or mask defects.
As Scott suggested above, if you actually remove the defects with the polish, then there is nothing left to be filled. I think Todd and Dave were suggesting that these lubricants/oils fill as a side-effect, not by intent, although clearly other posters referred to these as "fillers" as in, intentional fillers. I believe the reality is somewhere in the middle, the manufacturers need the lubricants to lubricate, and if as a side effect they also fill what's left, most polish mfrs. would consider that a plus, rather than a negative.