Rengar's bug with Statikk Shiv

So I ran four tests with 514 ad, the build was ie, shiv, ravenous hydra, duskblade, black cleaver, youmuus with 3 infernals, 1 stack of passive, and 9 ad marks with 3 ad quints. Dummy #1: Ult for guaranteed crit, with shiv proc and duskblade. The damage done was 1091 with a leap. Dummy #2: For this one i ulted for a guaranteed crit, walked up to it, and auto attacked it without shiv/duskblade. Damage done was 807. Dummy #3: This is where it gets weird. I ulted for a guaranteed crit, walked up to the dummy with shiv AND duskblade, doing 1214 damage. I did not leap for this one. Dummy #4: I ulted for a guaranteed crit then did a leap with only duskblade, and dealt 1008 damage. Dummy #5: I ulted for a guaranteed crit then did a leap with only shiv, and dealt 890 damage. Dummy #6: I ulted for a guaranteed crit then melee auto attacked it, and dealt 1013 damage. So, what I see happening is that Statikk Shiv deals the normal damage (160 bonus magic damage) when you leap even if you crit, whereas if you melee auto attack with the shiv proc and get a crit it deals the full damage. Is this intended or is this a bug? Thoughts? https://www.reddit.com/r/Rengarmains/comments/6xobx4/rengar_statikk_shiv_bug/