For Your Entertainment...

If I'm guessing correctly, this effect will apply to any summon that has a ball-type projectile - in this case Arrow Platter's bow is the summon, and the arrow is the ball. In contrast, for example, Frostprey/phoenix/Octopus/Ifrit are summons but have no ball-projectile for attacking, while attacks from you are not from summons therefore are not affected. I believe this is something KMS didn't foresee when coding, because I think they coded Xenon's Hologram to affect a summon's ball-projectile but here it affects all summons' ball-projectiles since it's not character/ID-tagged.

Hadriel