This is very interesting. Since I am an IDI, I find it especially interesting.
I personally don't think getting though locked doors or windows is a problem for professional criminals, so maybe the JBR intruder came ealry, maybe not. I can see it going both ways in my mind.
Maybe some of you recall the murder of Valerie Percy,daughter of Senator Charles Percy in '66, which is still unsolved although it could and should be. This was where I grew up and i lived not very far from the Percy home. Anyway, the night before she was murdered, we had an intruder in our home, he crept through the second floor while we all slept. My father inadvertantly scared him away, he heard someone in my mother's dressing room. He left through a window.There tool markings on the screen, a footrpint in the flowerbed and a bent gutter where he hung to drop from the 2 nd floor. It was ultimately determined that our intruder was most likely the same intruder that killed Valerie Percy. There were many simialrities and at least the LE made that connection. The break in at our home helped further the investigation, but still the murder has never been solved.
Like Boulder,the town of Kenilworth probably had very few, if any, murders so this was something LE was just not used to handling.
That unsolved case often reminds me of JBR only in that it really should have been solved, but the LE just wasn't equipped to handle a case like this. IMO.At least they checked out our connection for simialrities throughly.
A case like the one referenced should have risen right to the top for the JBR investigation and that is a real concern.
ETA: I should also add that the Percy family went into seclusion in California almost immediately after the murder, even though the murder was in Illinois. So, innocent people do sometimes leave town right away after their child is murdered. They relayed any information to Illinois investigators through their "associates" that is, not personally.FWIW