I know you're not knocking her. This probably won't be received well here, but the lack of precise physical description makes me think that early on maybe they weren't looking for her as a live, missing person or for "when did you last see this woman?". Maybe they already knew or had a good idea of where she was or what happened. When they were searching the trails and growth, there wasn't a need because she either would have been found or she wouldn't. Not sure how else to word this but in the beginning, any female found alive or deceased would be easily identified.
I know what you're saying regarding height, weight, hair color, etc. Maybe they didn't want to restrict anyone's memory by giving a definite description other than her photos. People might discount seeing her because to them, she didn't look as tall or blonde or fat or thin like the description said. People misjudge and misremember. A 'missing woman' lets people be open to a wider memory and no preconceived idea of what she looks like other than the photos. Broadcast that she's 5' 11" 105 lbs and people will still swear they saw her, but "she was so much shorter and stockier than described".
I also think that if she looked significantly different than the photos on the flyers, either it would have been mentioned or more recent photos used if there are any.
I
think those things, but I have no idea why they haven't described her in a traditional way.
If they thought it would help, I feel sure they would have described her in those terms when they asked for information. They know what they're doing.