Startup frames on block? SSF4

Hey, was j/w if blocks have startup frames? The reason I ask is because I noticed if I hit my opponent with move X and gain +6 hit adv i can link into move Y, a move that becomes active on its 6th frame.

This means my target would be at 0 frame disadvantage after move X but yet cannot block move Y. Is this because blocks have like a 1 frame startup?

The combo i’m talking about is chun’s far standing lp into far standing fp

You have 6 frames of advantage

You’re hitting ON the sixth frame

You’re hitting while you have frame advantage