Actually I don't think that's correct. An erection is caused by blood flooding the vessel in the first place. Flaccid seems to me that it wouldn't have much blood at all.
The only problem I had was the color of the blood.
But then I saw the end part and I just can't see how that's faked.
Edit: Oh, it's late and I misread.
He does look flaccid to me though, so I don't think there'd be a lot of blood.