There are just as many studies that say it isn't. And, IMHO, if you haven't been there and experienced it you don't have a fucking clue anyway. The texture, feel, smell is TOTALLY different based on the ladies I have experienced it with.
Although, I would be willing to agree that there are probably some out there who fake a squirt with pee. In fact there was a lady one time who wouldn't squirt unless you told her in advance that you wanted to experience it. WTF was with that? I figure she was just withholding pee in order to make it happen.
But overall, the ladies who can really do it ---- it ain't pee.
So the debate still rages. Although IMHO, a majority of the ones who are crying it's pee are probably those who have never experienced it.
Of course it's piss. Did anyone doubt this? There is no gland holding some special jerk sauce in it like males. The only organ down there in females large enough to hold such a volume of liquid is the bladder filled with piss. It would be like a guy pounding his pud while he's taking a piss and claiming he ejaculated a pint of cock custard. No, its yellow and clear - piss.