I don't think it is out of the realm of possibility that there was another perp in the house with Kohberger. I find Kohberger's (alleged) question upon of arrest of whether anyone else was caught to be meaningless. If he did what he's accused to have done, he's a sociopath and those people lie without remorse and love nothing more than feeling superior (such as by sending authorities on wild goose chases and/or pretending to have inside information) so it wouldn't be out of character for that to just be a bluff.
That said, it would not be without precedent for there to be multiple disaffected young man breaking into houses to commit stabbing rampages, as that
has happened before.
In this case, four college kids were fatally stabbed in under 15 minutes without the victims being restrained or bound and without causing enough noise to cause immediate alarm. It is certainly possible that one prepared man could pull that off but it is odd.
It is also odd that the probable cause hearing has been put off so far into the future. Generally the defense attorney knows s/he is going to lose a probable cause hearing but wants to have the hearing as quickly as possible so the police are locked into their story. His lawyers is apparently regarded as being very good, so presumably there is some reason for an agreement to such a lengthy delay. (I say this knowing nothing about Idaho law other than basic US constitutional criminal law.)
It would not surprise me if the delay is intended to create an opportunity for Kohberger to exchange information about the crime in order to take the death penalty off the table and to give the prosecution time before they have to subject an officer to cross examination.
That does not actually mean that someone else is definitively involved, more that the prosecution might have reason to think there might be at least someone else with other than incidental involvement and are willing to parlay inside info for a reduced risk of the death penalty.
Or I could be completely mistaken. I would bet it was a one man job but not heavily at this point.