Projectile Terrain Chain does not apply to ground targeted Skills

For example, Explosive Shot [Crossbow], and Gas Arrow [Bow].

Neither of these skills chain from the terrain with the Support gem that allows them to do so [Ricochet]. Why can these skills be supported by this if the interaction does not happen?

I noticed something similar. I have 50% chance to chain of terrain and explosive shot chains sometimes. it chains maybe 5 or 10% of the time. Though it chains off of the ground as well. That's a neat interaction.

I am playing a ranger and have socketed scattershot so my explosive shot shoots 4 bolts. But I get 1 chain every 4 or 5 uses of the skill when I would expect about 2 chains per use.