Is there a reason Gnar's Hyper doesn't have an on-target cooldown?

I mean, looking at the ability:

• Stacks are applied by both Gnar's autos and his fairly long range slowing Q.
• Deals a significant chunk of %HP magic damage on a champion who otherwise deals physical damage.
• Grants Gnar a fairly significant speed boost every time it's triggered, which is kinda amplified by his Q also slowing you.
• Doesn't require Gnar to build any specific stats to make use of it to its fullest.

Is it just that Mini Gnar is "weak" enough to justify Hyper not having even a small cooldown per target, or is it because it's a ranked ability rather than an innate? I say that because, overall, Hyper's kinda like Ekko's passive when you consider Mini Gnar's overall functions, in that it's a 3-hit effect that deals a good chunk of damage and can haste the user, and can be stacked by a skillshot Q that slows targets.