Spellthief's Edge disable passive bug

Was playing as Karma against a Zyra yesterday, and I noticed that my Spellthief's Edge passive was being disabled whenever I killed one of Zyra's plants, as if I'd killed a minion. I don't know if this was explicitly intended as the tooltip does specifically state that minions will trigger the disable, but says nothing about stuff like Zyra's plants, Heimer's turrets etc.

I can only confirm observing this against Haunted Zyra plants using Spellthief's Edge, on Lotus Karma, but it was definitely the plants triggering the passive disable.