Bard's ultimate and Zac's ultimate - frustrating interaction

I picked up Zac during free week and bought him and absolutely love him, but there's one thing that really makes me feel cheated when I play him. Bard's ultimate interrupts Zac's ultimate.

I understand that timers keep going while you are frozen by Bard, and I think that's fair. The problem is that Zac's ultimate is not on a timer as far as it is worded. Here is the description for Let's Bounce: Active: Zac leaps into the air, dealing magic damage to enemies within 300 units, knocking them back for 1 second and slowing them by 20% for 1 second. He then bounces on the ground 3 times, dealing the same damage and effects for each one, but enemies hit more than once take half damage and are not knocked up. Zac gains an accelerating movement speed buff (20 - 50%) over the ability's duration.

I bolded the key part there. Let's Bounce is not a timer - it's about how many times he bounces. From a coding perspective I'm sure it's based on a timer and so makes sense for Bard to stop him ins his tracks. The problem is that the wording does not imply it at all and that makes it totally frustrating for me to get frozen in place after 1 (or even 0!) bounces only to find out I don't get to do the rest of my bounces. I'm just stopped. No damage. No knockup. Just a 100 second cooldown on my ultimate.