While it's easy to see the possibility of confusing shots and bat as almost "common cause" at this stage, I'm not sure that this was the case at the time Dr. Stipp testified, nor that it was something the state would have happily conceded then. They went to the trouble of establishing Dr. Stipp's familiarity with guns, after all, and hence the implausibility of him confusing the two sounds. It was almost as if they hadn't considered the problems it would raise for their case for there to be two sets of gunshots, which considering they must have known what the witnesses were going to say, is very odd.
The reasons I see Dr. Stipp's admission as a win for the defence are two-fold: first, it opened up the possibility the shots were first, and so the screams can't have been Reeva (remembering that the earlier witnesses had only heard screams and then shots, a much stronger position for the state); and second, it tends to undermine the reliability of their witnesses: if the Stipps were absolutely convinced at the time that they heard shots, and yet were wrong, what does it say about their reliability generally? Might they have been wrong about hearing a woman as well? Sure, they were certain about that, but then they were pretty certain they heard two sets of shots as well... Even if it can be seen as a neutral point now, at the time I think it was very important for the defence to get that admission from Dr. Stipp.
On the timing, yes I agree, that's certainly one of the things (along with the stomach contents) that bothers me about the defence case. I must admit I haven't looked at it in much detail yet, except what I've read on here. So here are a couple of questions for anyone who might know: firstly, doesn't OP HAVE to be wrong about Reeva breathing when he found her, regardless of whether the shots came first or second? If she only took two or three breaths, then surely she can't have been breathing by the time he got to her, even if it only took, say, 30 seconds. Second, and in some ways a similar question, isn't it also very likely her heart stopped beating before she was taken downstairs?
If the above points are correct (i.e. Reeva stopped breathing and her heart stopped beating while she was still in the bathroom), is there still a problem for the defence about how long Reeva was alive after the shots?