This is false. There is no special "extra frame to come out of block stun" as some say.
Reversals remove one frame of block stun, that is a special property of reversals. Normals are not affected whatsoever from block stun.
After LK does Flying Kick MB followed by b12 doing a 6f normal will win clean, while a 7f normal will trade.
And as you can imagine, after Flying Kick MB, 6 or 7f normals will beat f213 clean, while 8f will trade.
So just to clear up the misconception that still is going around, there is absolutely no characters in the game who cannot trade with f213 after Flying Kick MB. However f2 has very high hit stun when trading, so it's doubtful that the 8f move helps.
To be very clear one last time:
Liu Kang only has a pseudo block infinite on Erron Black, Kenshi, Takeda and Jason while they do not have meter. This is a pseudo block infinite because a trade can still occur with an 8f normal. Every other character in the game can cleanly poke out of Flying Kick MB into F213 if timed properly. Several characters with 8f at fastest moves can use a low profile move in lieu (Kang
) of a fast poke to escape. Such as Johnny D4, Kano d4, etc