I suppose the bug is that the names don't reflect the kind of damage you'd expect.
I'm not an authority on the subject, but I'm pretty sure chain shot was meant to snare and break masts, which would probably result in collateral damage to the sails if you hit, or light damage to the hull if you shot too low. Grape shot would bounce off the hull or mast harmlessly, but could decimate both sails and any exposed crew on deck.
How are Templars like snails? Both move slowly and leave a trail of ichor behind wherever they go.
How are Templars different from snails? Ask one and find out...
I have never once seen grape shot damage crew. It always damages sails and hull, sometimes mast, sometimes cannons, never crew. I've been making a point if using it recently too so its not just a small sample size. Also, I have noticed it routinely one shot the enemy's hull, which I've never have happen with any other fore type. Grape shot should not damage hull at all imo.