This isn't a unique situation. My sister's new-construction home came with a recirc system, installed "retrofit" style (no dedicated return line) AND no thermostatic (4-way) valve (in a million dollar home, they scrimped on $20 worth of PEX to run a return line!).
When the recirc pump was off (running on a timer), the bathroom at the end of the line (where the hot-cold crossover occured) would get warm-to-hot water out of the cold taps until enough cold water was run to flush the line. If you had the misfortune of being in the shower in that bathroom when the pump came on, you got scalding water out of both taps and no way to regulate it.
