In Game bug with Ezreal and Bard

If ezreal cues up his ulti, and Bard freezes him in his Ulti right after ezreal cues it up, Ezreal's ulti continues to go off even while he is frozen in Bard's ulti.

Can reproduce by landing Bard's ulti on Ezreal just as Ezreal starts his cast animation.

Unsure if this is "working as intended" or is truly a bug.