It is important to wait a little bit so that gases in water come off before adding any developer ingredients, because there is quite a bit of dissolved gas in tap water because of the pressure, and oxygen may compromise developer shelf life. You can see how the gases bubble out when you leave it for a while. At 50 deg C, this happens in just a few minutes.
This may not be your problem here, but just a reminder! When I erroneously mixed C-41 final rinse concentrate instantly in warm tap water that still was bubbling a lot, it produced a non-clear, gunky solution I had to discard. Haven't seen the same with developer but maybe it's possible.