A previous CTO at my company would do this and it always weirded me out. Standing at the urinal, and suddenly hear him talking to a customer over in the stall. Very strange and uncomfortable.
I won't lie, though, I secretly enjoyed timing flushes to match when he was talking.
> timing flushes
Or porcelain-shattering dumps. Such a liberating experience by itself in a public bathroom, doing it to someone on the phone would give me a memory that would bring a smile to my lips for many years.