Sounds like what you're saying there is that the online is flawless for the game design, and while theoretically something could happen it wouldn't anyways.The punish window does not get smaller online. You have to input the command 3 frames sooner because the built in delay shifts it 3 frames, and you have 5 frames of buffer to help make it all easier.
The only way a window could get smaller is if a massive rollback hid an attack so long that you never saw any of the startup, active, or block stun frames and they magically teleported into their own punish window. Not even the fastest moves in the game could have all that clipped by the max rollback size for online. It's technically something that could happen with a rollback, but not for this game and the way it implemented it.
-20f is super punishable, but it is also pretty quick in real world time. If you aren't sure what's happening, what your options are, are kind of sloppy, or generally not well versed in what to do, that window is supposed to slip by on occasion. You have to prove you aren't letting them get away with dumb stuff or they get to keep running you over with dumb stuff. That's literally part of the gig. Not the MK11 gig, fighting games at large gig.
I don't agree with that...but i think we could agree that ideally you gotta punish as soon that block contact occurs.