I’ve noticed this too. Furthermore, since I am not using a Pozyx system I had to adapt the arduino code to make my Decawave hardware appear to be a Pozyx system to Ardupilot. Doing this I remove the two stages you are talking about, because I could not understand what its function was. So my system is always refreshing positions only at 0.5Hz. You can see this in the logs I posted here:
https://discuss.ardupilot.org/t/ekf3-large-position-offset-after-startup-using-uwb-beacons/85037/11
If someone could explain in more depth how this code works, I would appreciate it.