Vi losing CC immunity too soon during ult?

So, having my go at Vi again after the bugfixes and QoL changes in the most recent patch. The problem is, I'm losing my CC immunity from Assault and Battery at the end of my charge but before my target is knocked up. Things that have CC'd me in these instances: Buster Shot Shockwave Dark Binding Glacial Fissure/Winter's Bite

Is this an intentional but undocumented change, or did Riot add one bug when removing another?