I remember missing that Jab, delaying my Guard by one second. I actually never cast that Guard...
Personally i'm not advocating hard cap, but i fully understand those who hard cap their Brewmaster on single tank fights for various reasons, or fights that do not require tank swaps (i do question the usefulness of hard capping on fights in which you spend half your time behind the boss though).
Actually it's a bit more than that. The Jab you cast instead of KS can miss too, resulting into a further loss of 8 energy and 1 gcd.If you miss a Keg Smash and you immediately follow it with a jab all you have lost is 1 chi, 8 energy, and 1 gcd.
Not so bad. Missing BoK gives Shuffle anyway, you just lose the damage (plus a chance to proc Gift of the Ox and your weapon enchant) if you miss.missing Blackout Kick = bad