The timing on when to start the unblockable is so late that it seems hard to do.
And have you tested it against teleports?
I've actually found that you have enough time to dash after the f+4 and start the b+2 charge and the opp still can't interrupt (because the dash cancels part of the recovery of f+4, I think).
And yes, tested against teleports. There's only a couple of frames to interrupt, if that, even Kung Lao's spin can't interrupt. An armoured teleport gets out, though, obviously.
I tried to interrupt with Kung Lao's spin, his uppercut, and his d+1, and none of them worked. To my knowledge, those are some of the fastest moves in the game.
EDIT: I was gonna make a big(ish) video about it, but I don't want to go to all that effort if it turns out there's something I'm missing and it actually isn't legit (part of me feels like maybe because PSN is down the game can't run version 1.01 at the moment, but that seems very unlikely). So I'll just make a quick vid to show it, so that people can see what I mean, and then maybe you can test it yourself and see how it goes.
EDIT2: Here's the vid:
For some weird reason it's in like half-speed... But you can see me mashing away in the corner, and not being able to interrupt.