Recesses are added to eliminate blind holes

I suspect that a blind person would rather not be blind. Threaded holes in die castings don’t want to be blind either. Blind threaded holes in die castings have more quality issues than through holes

STRIPPED THREADS

Cast bosses for creating blind threaded holes must be larger. This makes them more likely to be porous. It is more difficult to achieve a strong thread in a porous boss.

LEAKERS

Form taps without vent grooves like to hydraulically punch out the bottom of blind threaded holes

BOTTOMED BOLTS

Blind holes have the potential for creating a joint where the bolt is not tightened properly. For example a dog point can rest on the bottom of the drilled hole

EXTRA MACHINING OPERATIONS

A bottoming tap may be needed to created good thread that is deep enough

Die casting is a versatile process. I have pictured an example of a front engine cover that originally had blind threaded holes. Pockets were added behind the bosses to expose the back end of the threaded holes. In most cases this type of design change must be requested within a week of being awarded the casting business. This improvement also saved a CNC machining tool change. I no longer required two different lengths of step drills. The icing on the cake was that 100% leak testing went away.