Geometry shaders have long been disfavored by all ISVs , not just Apple. It’s just most include the software path.

If you’re using geometry shaders, you’re almost always going to get better performance with compute shaders and indirect draws or mesh shaders.

A lot of hardware vendors will handle them in software which tanks performance. Metal decided to do away with them rather than carry the baggage of something that all vendors agree is bad.

It takes up valuable die space for very little benefit.