Many woods are stronger in the neck of an open handle if it runs fairly straight down the neck. Some are strong enough regardless.

I made a lot of handles from various woods once just to break them, to see how they failed and where, neck, horns and hand hold areas.

The Oaks and Ash were simply pretty strong whether they were flat sawn or QS, grain running straight down the neck or off straight depending on the thickness of the stock and the width of the neck.

Closed handles can be near any orientation as concerns the connectors between the cheeks and hand hold.

The thinner or more delicate the handle, the more important the grain orientation is regardless of the wood.

Take care, Mike