It's not glitchy, it's due to input buffer/leniency. Like in this game you have to input a string or a cancel, similar to a "dial in".
An example of this is how attacks after a jump in work - you have to hit the button after you hit your j2/4, while visually, your character is still in the air, in order to combo. Meanwhile, in games like SFV, you can hit your button after you visually hit your jumping attack, meaning you have more time to press the button.
It works the same way you press buttons to get a combo, for example take Raijin in the corner, launch your opponent with DB4(AMP) 1 B12 DB2. If you press to early, only the 2 will come out, so you have to time it, you can't mash it.
In reality it's math.