[gameplay] irelia appears to be stunning champs with E even when she has higher % health than they

Was playing ARAM (as vayne) vs irelia. Once she E'd me and stunned me and I thought, "really? I coulda swore her % health was higher...". A second time she was at full health and I was maybe 80% and she definitely stunned me with her E, rather than the E applying the slow. repro appears to just be "irelia has higher health % and hits you with an E" but I haven't experimented.