Taking the simple view, the intent is probably to try and avoid shutting down an engine (which is often not time critical but very critical on getting it right) during a period of peak workload and essential monitoring, like an emergency turn and/or terrain constrained departure. It also helps the aforementioned turn/departure go according to plan as well.
If you were operating at optimum+ altitudes in the cruise, it might be sensible to sort out where the aeroplane is pointing before securing the engine as doing it the other way round (or attempting both at the same time) could cause problems.
I have seen the phrase “...only when a safe flightpath is assured” mentioned in quite a few manuals when describing some non-normal procedures. I think that is generally sage advice...