Isn’t it actually more accurate to say that they _can_ delegate power and while unconstitutional, it remains in effect until challenged by the judicial branch?

I disagree, it is worth talking about because the impacts of delegated decisions made impact real people in meaningful ways while those may or may not be challenged in court. To say a branch can’t delegate absolute authority is also a mischaracterization of reality. Assuming orders are challenged in the first place, it often drags on for many months or years leaving the impacts in effect until that concludes.