I suspect the reason for the rush to judgement about murder/suicide is because police are always attending 'domestics' and when a woman or man is murdered, esp in the home, its more often than not the spouse who did it. They didn't 'just' say murder/suicide, they supposed a double suicide as well but that didn't 'catch on' as a possibility. I also do not really think it was a judgement, just loose lips sinking ships. of course the media wants something sensational, something that sells papers. IMO
If there was doubt about what happened there, LE would have called in homicide right away and took many more precautions. They still haven't labelled this as anything more than "suspicious".
I doubt that their gender was what they based it on. One male, one female, must be domestic.
There is likely something very, very glaring and obvious, like one partner beaten, and one partner showing knucle injuries. Perhaps bloody footprints of one dragging the other with the bloody footwear still on the wearer. Perhaps an item from the home was used to hit the other and was found with bloody hand prints or fingerprints on it. Perhaps there was a message scrawled on a body or a wall.
There is always the possibility LE will suddenly charge someone and allege they staged the scene, but it doesn't seem likely. There are no real telling signs that's where this is heading.
They will likely wrap things up at the home, wait for toxicology results, put everything together for a PR type announcement, and then wait for a busy news day to release their findings so that it won't be the lead story for a week.