Its called Block Stun..... TN can make a move safe or unsafe by changing how long the opponent is stuck in the blocking animation without having to change the actual moves themselves. If you want you can even calculate the blockstun.
They're not the same move. 6K deals 20 dmg & PP6K deals 23 dmg for instance. A lot of moves have recovery around 22-25 frames.
If you want you can even calculate the blockstun.