Vet is wrong.
Chances are it was calculated incorrectly, not taking into account that the transition into a stun state from a non-stunned state takes priority over
everything except normals.
For example, against Satsuki 5A, which has 4 frames of startup:
- Inputting '4' exactly 4 frames after 5A results in a successful block, since blocking has no startup.
- Inputting '2Q', '5Q', 'D', or '214D' exactly 4 frames after 5A will not work. Why? Because getting knocked into stun takes priority. You'll just block or get hit depending on which direction you pressed or were holding on that frame.
- However, inputting '214D' or '5Q' exactly 4 frames after 5A but during blockstun (or hitstun) will intercept the 5A just fine. It works because, since you're already in blockstun, there's no stun transition frame to take priority over your inputs.
As for backdash;
- Inputting it 2 frames after 5A avoids it
- Inputting it 3 frames after 5A gets you slapped in the face
- Inputting it 4 frames after 5A will cause the game to ignore the input, and you'll just block instead due to pressing 4
Represented in a visual form:
SSSSHHHRRRRRRRRRR <- Satsuki 5A : Startup, Hit, Recovery
__SSDDDD... <- Good backdash
___SSDDDD... <- Bad backdash (5A hits the second frame of startup)
____SSDDDD... <- No backdash (Stun transition takes priority. Registers as high block due to pressing 4)
_____SSDDDD... <- Late backdash (You get hit before the input registers)
2 Frames of startup. That is all.
(edit: forgot about normals; the stun transition doesn't take priority over 5X and 2X, just everything else)