You could say it is worthless anecdotal evidency, but I would beg to differ in at least a few cases. The fact that you can not have a single girl (from the normal pool of the bosses) drop with over 800 fights is rediculous. If they were adding a hardcap, then it should be significantly lower than 800 fights. If you literally use every combativity you get, that would be 50 per day (I could be wrong here, but for arguments sake). That means it would take you 16 days to drop 1 out of 3 girls from a boss. There are 8 bosses, so if it took that many every time it would take you 384 days to get them all. This is not counting any event girls or similar things.
I'm not sure about the rest of you, but I intended to use kobans to get the pachinko girls, but before you have all the boss girls, there is quite a large chance that you "accidentally" get one of the boss girls. This means that in order to avoid getting boss girls, assuming you aren't lucky and don't need to hit the hard cap, you would need to farm, literally all the possible energy you get for 384 days before you can even start using kobans to get the pachinko ones.

This doesn't take into consideration that by the time a year has passed, there is more than likely another boss added and considering the new "legendary" girl, perhaps even a new mechanic(s) introduced that might take some of that energy.
My point is, if you're looking at it from the standpoint that you perhaps wish to gather all the girls, unless you are willing to sink massive amounts of money into the game, it is just unrealistic to obtain. This discourages players from paying anything at all, because as it is, you are quite likely to be "wasting" that money on something that others, who are lucky, can obtain for free.
Perhaps I am mistaken, but the way I see it, this seems like a poor business model. That's just my 2 cents.