His objection wasn't to him reading the full AA (he did approve the arrest warrant after all), it was to the fact that the AA has to be publicly disclosed at some point. Including all of the extraneous, prejudicial information meant that either that information would be disclosed to the public or the court and the parties were going to have to spend a lot of time going back and forth with motions over what parts would be redacted and what parts wouldn't.
I think it's important to remember this whole case was on an accelerated timeline as soon as the prosecution filed their complaint. In a first degree murder case, it's quite normal for the defendant to waive their right to a speedy trial. Normally the defense is at a major resource disadvantage compared to the prosecution and they need the extra time to prepare for trial.
BM's lawyers quite cleverly don't appear to have waived that right. They seem to have gambled correctly that a compressed timeline (6 months) would be more of a problem for the prosecution than it would be for them.
I think that time pressure informs a lot of the judicial decisions in this case. Judge Murphy couldn't take the time he would have liked to properly redact the AA because they needed to get to the PH. Judge Lama couldn't just delay the trial to allow more time for the prosecution to prepare their expert witness reports and for the defense to read and respond to them, etc.