Reaper cone attacks have narrower permitted attack angle than the damage cone

The two Reaper cone attacks, Grim Swathe and Guillotine, hit a 180 degree forward cone. However, they have the same restriction as other 90-degree-cone abilities on usage, in that they require your target to be in the "forward" angle (90 degree cone centered directly ahead) in order to be used.

This can be replicated by having two target dummies next to and within 8 yalms of each other. Target one dummy and place your Reaper directly in front of that dummy, so that the second dummy is slightly ahead of directly to your right or left. This places it within the 180 degree forward cone, but not the 90 degree forward cone.

Target that second dummy. Observe that neither Grim Swathe or Guillotine can be cast with that dummy targeted. Now target the first dummy, the one directly in front of your character. Cast Grim Swathe, then Guillotine. Observe that both attacks still hit the second dummy, despite the game not permitting you to cast the cone attack with that dummy targeted.

Intuitively, the attack should be usable as long as the target is within the cone the attack hits. To be honest, I'm not sure why cone attacks have a target requirement in the first place (they're AoE attacks, after all, and neither point blank AoE attacks or ground-target AoE attacks require your target to be within the range of the attack. In fact, they do not require you to have a target at all). I'd love to see the target requirement on cone attacks entirely removed, across all class (bugs the heck out of my on Warrior too). But if it remains, the two Reaper cone attacks should at least have a target restriction cone that matches their actual attack cone.