it probably gave s, the problem is usually RC is pressed too early so their attack is still active. what should happen is their meaty attack whiffs from the super invul + RC slowdown allowing you to react and punish them. RC has a few frames of startup and it cancels your invulnerability so if you press too early they still hit their meaty in this particular case slayer's c.S doesn't look like a meaty at all so they mistimed it which allows them to catch FAB doing PRC
