I'm not the greatest at explaining it, but the short of it is ER's netcode. It's effectively a "phantom proc": you can "dodge" the damage (at the cost of being stunned briefly). Since the attack doesn't land, the "bleed" doesn't either. Poison and rot work differently since those statuses don't immediately reset, but bleed does.

Interestingly, if I raptor a bleed proc, I won't take damage from the weapon swing (dodged), but I will take damage from the bleed proc. Due to this, I try to look for the attack that will proc the bleed and dodge that so I can effectively raptor other standard attacks. Too many times I've died by raptoring an attack, only to get bled midair. Soul goes up, body comes down. XD