I think BF/DM didn't see Xana, HJ is the only one who did and didn't give details to BF/DM. Been thinking about what HJ might have seen or not, and I've changed my mind. He did see...and was not telling the girls, IMHO.
Here's why:
The transcript is hard because there aren't time stamps on each line, and at many points it appears that people are speaking over each other (like other first responders later in the transcript) and some lines seem like they are things that are heard on the 911 tape not because that person is currently speaking on the phone but because they are heard in the background.
According to the transcript and what we glean from reading:
A: answerer female DM or BF
A1: another female answerer, who identified herself as a neighbor
A2: answerer male--HJ
For the first part of the call we've only had the voices of DM/BF and the neighbor both directly speaking on the phone or heard in the background. Then dispatch starts pressing BF or DM on whether or not their roommate is currently passed out/cutting her off before she can explain what happened in the middle of the night.
DM/BF seems to indicate that they are going to physically head back to the house/to the room to check. IMHO, it seems like HJ comes out then, DM/BF sees his face and is asking him what's going on/what he saw. She then puts the phone in HJ's hand after stating Xana's age:
DM/BF: "Yeah, I'll come - come on. Let's - we gotta go check. But we have to. Is she passed out? She's passed out. What's wrong?"
Dispatch: "Dispatching Moscow Law ambulance for..."
DM/BF: "She's not waking up."
Dispatch: "...unconsciousness, 1122 King Road."
(bunch of dispatch two different first responders talking over each other)
HJ: "Yeah. Yeah, it's (Evan)." (IMHO, heard in the background of DM/BF being on the phone. I think he might have said Ethan)
Dispatch: "20 you said?"
DM/BF: "Yes, 20, here do you wanna talk to 'em?"
Dispatch: "Okay."
HJ: "Hello? Hello?"
Dispatch: "Okay. I need someone to stop passing the phone around because I've talked to four different people."
HJ: "Okay. Sorry. They just gave me the phone."
Dispatch: "Is she breathing?"
HJ: "Hello?"
Dispatch: "Is she breathing?"
HJ: "No."
----
HJ: "(Bethany) or (Dylan) I need you to - to talking to them, okay? I can't talk to them. I need you to talk to them."
the phone then goes back to DM or BF for the rest of the call
****
HJ, who was Ethan's friend summoned by the girls to help, is the one who went in the house and to Xana's room. This is all IMHO, MOO:
HJ is not present for the first part of the call. He went up, saw that Xana was dead, calls or texts DM or BF telling them to call 911. He doesn't give them any details AT ALL. Literally just something as short as "Call 911 now!" So when DM or BF call 911, they are only operating on what they knew--they'd been calling and texting Xana, she wasn't responding, maybe drunk and passed out--hopefully?
Actually, note that the neighbor is the one who tells dispatch that Xana had been drinking the night before/passed out/not waking up. Even when dispatch asks DM or BF just a few seconds later if X is passed out, DM or BF answers that they really don't know. I imagine the neighbor isn't really clear at that moment on what BF and DM had told her happened the night before. Drunk and passed out is the neighbor's interpretation.
After HJ has come out mid call and BF/DM senses something is wrong from the look on his face/a response that isn't heard on tape/a headshake, I think BF/DM shoves the phone at HJ--hoping that since he had just gone to check on Xana, he would be able to give dispatch better details than she could.
But HJ, imho, is in shock. But when dispatch asks if Xana is breathing, HJ answers unequivocally "No."
If HJ is saying that, it is because he either got close enough to Xana to see that her chest wasn't moving or he got close enough to see enough details that he knew she was dead and way beyond the help of an ambulance. Does he know how to tell the girls that right then, is he just horrified beyond belief, can he even imagine telling the girls right there standing outside the house that Xana (and probably everyone else) is dead? Does he figure it really doesn't matter if 911 has specific details right now---because from what he saw there is nothing an ambulance can do?
As soon as he can, he tells the girls he can't talk on the phone.
It appears to me that shortly after that, more than one first responder arrives. I think HJ takes one of them away from DM/BF (they are still on the phone and talking to one of the officers who has arrived about a defibrillator) and tells him what he saw. Because just as soon as DM/BF get off the phone with dispatch, an officer tells dispatch that he thinks they have a homicide..and I think that happens too soon after first responders arrive for them to have gotten into the house and gotten to where Xana is.