I agree with you that it would make a difference. Statistics would suggest that it was probably either an individual known to her or an individual that knew her...even if she wasn't familiar with them. (ie: someone she may have seen on a regular basis but never spoken to or had limited contact with) But you can't rule out a stranger either.
If nothing can be ruled out, then all things have to be considered.
I tend to think a little differently about things. This is all just opinion, based on the facts of the case. I tend to believe that Holly probably had a different schedule nearly every day of the week. We know that at the time she vanished, she was going to classes at the school on Wednesday and Thursday. On other days, she was doing her practical nursing work in medical facilities.
From personal experience, I know that student nurses are often scheduled in at various times to give them exposure to working different shifts. I don't think it would have been unusual for her to leave the house at different times on different days.
That is why I think her abductor had to know her schedule. He had to know that she was coming out at about 7:45 that morning. She actually probably tried to leave about five minutes earlier than usual to get to the test, according to best guesses.
I don't imagine he knew she had a test that morning. If his purpose in going there was to abduct Holly early and flee before anyone noticed, he could not have known that classmates and a teacher would have probably gone and at least called Holly to find out why she was not at the test in a matter of minutes or hours.
I don't think he expected Clint to be there. This leads me to wonder if his initial purpose for coming there was possibly to sexually assault her. Maybe he hid his car and waited in the bushes. Perhaps he was planning to assault her when he drug her into the garage or accosted her in there.
When the little dog in the house was barking, perhaps Clint began telling the dog to "be quiet," and the abductor heard his voice in the house. Now there was a problem. He could not drag her in the house, as someone was there whom he had not counted on being there. He could not assault her in the garage, as the person in the house might come out and discover them. He couldn't leave her, because now she had seen him. The only alternative was to take her with him. I don't even think the abductor realized how many things Holly had with her that would later have to be disposed of. I think he panicked and threatened her or possibly threatened to kill Clint, and Holly complied to try to save the both of them.
I think it is highly likely that this person was a local who had full knowledge of her schedule by virtue of the fact that he had access to her school records and/or her hospital and class hours schedule and knew exactly when she would be leaving the house. Or, he could have been a close enough acquaintance that he knew Holly's personal schedule. As someone else pointed out, he had to know she'd be alone, be driving her own car (as opposed to catching a ride with her parents or a friend), coming out the back door as opposed to the front, etc.
The only other possibility I see is a random stranger abduction, in which case Holly just happened to be in the wrong place at exactly the right time for the perpetrator of this incredibly sad crime.
I think there could be merit to this theory from the standpoint that the camo man did not just immediately grab her and drag her into the woods. Remember Clint observed them having some type of conversation in the garage between Holly and her assailant. If someone were in a hurry to grab Holly and get her out of sight before anyone noticed, why would they stick around and have a conversation?
JMHO, as always