I haven't tried it, so I can't comment on it personally, but one thing to note is that any cologne or aftershave smells different on different people depending on how it mixes with their natural oils and stuff like that.
So it may be a case where it actually does smell like lilac in the bottle, but for most people when it hits the skin it changes into a less than pleasant odor.
That's just my 2 cent theory though which should be taken with a grain of salt seeing as I've never tried that aftershave.