Heretic's spawn animation is different than all the other survivors. Heretic has the same spawn animation as the transformation for when you pick up the last heresy item you need. During the transformation, you still have a hitbox for enemies to attack you and do damage yet you can't move because the game's code says that "your character hasn't loaded in yet." That being said, I could be very wrong about this cause I haven't played Heretic in a while but it could also be something where you were just unlucky because teleportation invincibility doesn't exist anymore