No icon-based forecast would predict only hail. Hail is a product of intense generally warm-season thunderstorms so if, for some reason, hail was in the forecast you would see a thunderstorm icon.
Sleet is formed in an atmosphere where there is a warm layer well above the layer of sub-freezing surface air. Snow well aloft melts into rain in this warm layer, then re-freeze to sleet or ice pellets. Sleet bounces too, just like in the picture.
(Hail is formed by intense updrafts within a thunderstorm which pull raindrops well up to a sub-freezing layer a mile or so above the surface of the earth. The frozen drops fall as the updraft weakens, but are often pulled back up into the sub-freezing level by other updrafts, adding a layer of water/ice each time as the hailstone falling into the rain/cloud and then gets pushed back up over and over again. Sometimes this process (with very intense updrafts) can produce hail the size of a grapefruit or larger.)
And the OP's icon is heavy, accumulating snow...as Frosticus said.
Maybe there's a way to extract all the icons from the iPhone OS and then we could analyze.
There is a strict order to weather icons and it should be possible to deduce the meaing simply by the order in which they are listed or named.