There are inward kickflips and heelflips just as there are varial kickflips and heelflips. The 180 rotation of the board is opposed for kickflip and heelflip because the "inward" refers to shoving the board to where your foot is also flicking off the board. Just google varial (kick)flip, varial heel, inward heel and inward kf. There are very detailed trickiest for each where you can see for yourself.
Inward KF = hardflip, the illusion flip method just cane wildly into fashion in the late 90s to where they were just very angled pop shove it's. by the mid 00s it was Sean malto et et who established the flatter and more technical method that Darwon pioneered. Heitor da Silva is bringing the vertical muskaflips back in an ironic steezy way.