Yes, you are correct. You CANNOT grab anyone out of Block Stun. If you could, you could just buffer Low Jab into SPD, and it’ll grab. No, you HAVE to wait until they come out of it to grab.
Now, the odd thing is that Gief feels like he has a WINDOW of grabbing, so even if you did it slightly early, it’ll start to whiff and THEN grab. You’ve seen it before when it looks like Gief twitches and THEN grabs. Now, I have NO scientific proof of this concept. It just feels that way from years of using Gief.
It doesn’t seem to work that way for Hawk. I don’t think he has that window, again, it might just be how it “feels”. But in any case, I too have found myself whiffing his throw a LOT, but that just tells me that in the days of ST, that’s probably why I ended up jumping so much when I tried to SPD with Hawk… I was actually doing it too early.
So just put a fraction of a second delay before trying the SPD, ESPECIALLY with the easier codes that take less time to perform. I find myself whiffing a TON with Hawk just because I do the SPD from D/F to U/B a lot now, and it’s SO fast.