I have seen 2 escort, who had squirting as a like, and it was for this reason I booked them, and I would say its not piss
The 2 escorts I had seen, very different squirts, one escort could squirt continuously where as the other one, it was only a few squirts
The first escort, her squirts, were clear, and had no taste, where as the other one her juice tasted like peach juice, now the common factor with both escorts, when they both ejaculated or squirted, there was an reaction in the anus, it would expand or contract