Cooling question. One side warm one side cool.

[Kawana]

I just finished doing a radiator flush, by sticking a gardening hose in each end and flushing till it came out freely and clear of debris. I replaced the thermostat with a slightly warmer one, and put everything back together and let it idle for 10min with some cooling system flush stuff and water mix as per the instructions. After 10min of idle, the lower rad hose was fairly hot, while the upper rad hose was cool to the touch. What could the issue be? I haven't taken it for a drive yet, only sitting and idling.

 

[90halfton]

Could it be that the lower hose is hot because of the heater hose flow that is going to the water pump for recirculation back to the heater core. And maybe the motor has not gotten hot enough for the thermostat to open?