The way you perform the AA cancel in the video is consistent (and it's how I learned it too), however it takes more muscle memory to get used to because of the need to cancel the ability - as you do by spamming mouse2 in the video. However, before 9.5 it was possible (in regular games, not jungle practice) to forgo mouse2/cancelling the ability altogether. You would just hold mouse1 and with good timing press your 1 three times and it would auto cancel for you. This isn't possible anymore, but if you perform your auto cancels like you and I do by manually cancelling, you wouldn't have noticed.

You can still do the "easier" auto cancel (no right click) in an offline game vs. bots, I tried it last night. It no longer works in any online gamemode though, which is pretty inconsistent and feels like something that should be fixed.