Not sure why you restrict this observation to UK and commonwealth countries. This is reality for many of us in Europe. Legal documents in Norway also refer to the king as the one deciding stuff. But that doesn’t literally mean the king. It is more of the institution of monarchy and the ceremony in which the king signs government actions presented to him by “his” government.

But this is of little practical consequence. What I find more bizarre is how conservative the US is around its constitution and political system. Norway may be a Monarchy but has gone through far more modernization in terms of how the political system works, elections and government than the US for instance.

I look at how voting and representation works in the US today and it is basically Norway in the 1880s or something. Back when we also had a two party system of liberals and conservatives. When there was a winner take all system. Censuses had to be done semi regularly as citizens were not fully and completely registered and kept up to date on a continuous fashion.

I would bet Britain in quite a number of ways is more modern in its constitution than the US. E.g. they don’t have å gerrymandering problem. That got reformed and fixed long ago.