It would seem Talon accidentally AA'ed Yi, if Ignite doesn't do it already (though can't see the AA animation even on slow-mo, maybe animation-cancelled).
The evidence is that the flying blades eventually all converged onto Yi rather than Talon, it only happened because Talon had broken his stealth and AA'ed Yi.
From the description of Shadow Assault:
When Talon emerges from invisibility, the blades converge to his location, dealing the same physical damage to all enemies they pass through. Breaking invisibility with a basic attack or Noxian Diplomacy causes the blades to converge to his target instead.
So yeah. I think the case's closed.