Twitch Ulti 0 Damage

I almost lost a game yesterday because when I went to backdoor a one or two hit nexus as twitch, I popped ult for range/damage thinking I might kill it a fraction of a second earlier or something. Instead I watched my auto attacks land on it and do nothing (sat there attacking it until they came and killed me many attacks later). This was at 45 minutes in or so, not when you can really afford to die for no reason, and I was pretty frustrated. I thought maybe this is part of the change to twitch where they wanted him not to hit both nexus turrets... But no, digging around I found a thread from 2010 with a Riot response about twitch ult not damage inhibs, saying it's a pretty bad bug and they are gonna try to prioritize this.

It's not fixed and it's seriously confusing! 5 years later it's still here and it very nearly cost me a game. The only way to know it works like this is to experience it. Which means it had a pretty good chance of screwing with your game. Game clarity is important, right? Full build adcs should damage buildings by right clicking them.