How does iOS and M1 interpolate half data from the Vertex to Fragment shader?

Want to use half data, but it's unclear how the A series processors handle interpolating it across the polygon. Adreno/Nvidia doesn't allow half in shader input/output due to banding. Mali recommends declaring half out of the VS to minimize the parameter buffer, and declare float in the FS.

Can Apple provide some insight as to best practices here?