The thing with this trick is a visual display of one skill, while you are actually using another.
In this case, Sorc is actually using Inferno, but Frozen Orb is displayed instead with FPA (Frames Per Attack) of Inferno. When performing Skill Bug all characters (except Paladin and Barbarian) do it while standing in one spot.
How does that help us in PvP, since it is just a "visual indulgence"?
The trick becomes useful with Paladin, the visual display of Blessed Hammer instead of Charge (and his FPA). It will look something like this:
Due to the fact that, after all, it's still a Bug, when we are Charging wear are really moving in a way (we don't stand in one spot). After running a short distance, we can make an unexpected stomp. It works somewhere in 2~ game screen from where you started the bug. For the opponent, it would look like stomp from nowhere.
Actually, this can be perceived as a Desynch. And, indeed, in theory, if you do the Charge+Vigor thing right and stumble at some holes, you can get something very similar. But then we will never be sure how good the desynch is, whether we froze in one place, or just moving around with a big delay on the screen of the opponent. The opponent can guess your pathway and attack us. So, in the end, it might end badly for us.
The thing with a Skill Bug is that we are 100% sure we froze on opponent's mini-map. Besides, we can't receive damage while we sprint to the opponent. During this time we are kinda ~immune to missiles. The danger may lie when your enemy caught you just the moment you performed SB. If he attacks you at that same moment, the damage will be received and your "true" location will be revealed. Personally, in my practice, that never happened. If the opponent flew to you it is a good opportunity for stomping him. Simply don't panic and just instantly stomp him first.
So, how to perform this bug?
Blessed Hammer on the left skill bar of CtA. Charge on the Hoto's left skill bar. Start Charging around. Right after click Swap > Swap+Hammer (bind on the left panel)>Shift (Stand Still). For Example: "R" > "R" + "Q" > "Shift".
Swap > Swap+Hammer >Shift is pressed quickly and clearly with the same frequency. Re-watch the video again and turn the sound louder in order to understand the frequency with which you need to perform this combination. It (the frequency) is approximately* equal.
*perhaps slightly belated Shift, as if the delay between the Swap > Swap+Hammer is 10 units, then Shift-click cam be done 12 to 14 units after the second swap
The indicator that you are Skille bugged will be that fact that your mana will no longer drain. Also, you will be returning back to the place where you started the bug (if you ran too far). There either won't be a sound of casting Hammer or it will be halfway "interrupted":
Run > Swap > Swap+Hammer >Shift
Mana is not draining, then we are in the Bug. We are charging to the opponent (or wait, till he comes to you). Stomp him.
Try it. After a couple of evenings (with some rest ofc, but totally about two hours per day), you should be already able to do it "over time". Soon your fingers will get used to that timing and will do everything mechanically and soon you will find a good application for this trick. Try to use it in regular PvP, but not too often. Anyway, trying it will take only a few seconds. If you failed (mana is draining), just continue your duel.
The second helpful usage of this trick comes with a Barbarian. We bug WW to Zerk. So while we stand in one spot on opponent's mini-map, we actually WW closer to him. That way we can make an unexpected lock while being two game screens away.
Good Luck and Have Fun!
Wish you good luck in all your endeavors!