Sivir's Ricochet, W ability seems bugged when aa towers

Entered an ARAM with Sivir. Game started normally, no hiccups. We siege enemy tower, I get into range to aa. At this point I activate W for the atk spd bonus passive from ult (at this point it's 10-20 mins. into the game). The Ricochet's (W) bounce off of tower and hit enemy champs and I get tower aggro because of it. This was after the 4.19 patch. I don't recall Sivir's W bouncing off of towers at all (note: it only bounces off of towers when towers are initial target with aa not from a bounce) in any game mode so was this changed? If not it's definitely a bug.