Only when A & B are both coming out of the bathroom can interaction occur. Otherwise, A is desperate and dashing in, B is wishing she'd not had that curry last night, or both A & B are desperate and not stopping for anyone ;)
I'd be interested to know how much they saved on plumbing costs. That seems to me like an architectural decision driven by financial concerns and sold as a benefit. Not that it isn't a benefit, many of the most interesting designs are a consequence of some practical constraint.
Maybe, but that particular mechanism was implemented. It actually received some negative feedback from a pregnant woman who felt she was forced to walk an undue amount to the bathroom.
The point of the parent was that the Pixar offices are designed around encouraging unplanned team member interaction. Their leadership believe this is crucial to encouraging creativity.