This test is IMO not a good way to test
@RM_NINfan101 's ability (or lack of) to fuzzy guard.
6f to 18f, both with very clearly different animations is much different than the ones being used in this test. For one, the test uses 4 different attacks, varying the difference in reactions greatly (2 lows, and 2 overheads). One of the lows has a very similar animation to each of the overheads because she first stands then goes back low, this is unlike Shinnoks animation. The frame count on these moves is also a lot closer than Shinnok's :\
A more accurate comparison would be the standard quick low poke she is using, and that slow, very seeable "moon" overhead (looks like a moon to me, idk). That is much more comparable to the situation we are describing where one move is very clearly slower than the other, and has a totally different animation.
Nobody is saying that you can actually have that fast of a reaction time consistently, but based on timing differences and major animation differences it is most definitely conceivable that one could fuzzy it (If i had to estimate i'd say a solid 70-80% chance on a straight up F4 / B3). I used the OH at Toryuken once a set, very very rarely, and people like
@Jer who have never seen the move EVER still fuzzied it first try lol. The move will hit inevitably some times in a match don't get me wrong, but saying that this F4 / B3 is a true 50/50 is ridiculous. You could do some things such as stance switch -> f4 to make it appear as a B3 attempt in the heat of the moment, or simply walking for a brief moment then going into F4 to try to cover the animation differences and then it becomes a whole different ball game; but this merely changes the dynamics of high/low block into poke the delay or overhead / dont poke and block the fast low.