This thread is great.
My opinion of the info is that it seems secretive because very few people care to have it. I can't speak to NH300 or the 3,000 footers, etc, but I finished the NEHH 10 years ago. Other than the TW72, my bush whacking really stopped there. My experience was to send a request letter to the committee. I was given an envelope with some pointers and details on approaches for each mountain as well as photocopied sections of maps. In many cases I bought the large USGS quad for the area and looked over possible ways and routes to summit. It was an awesome adventure and fun way to do it. It was not pre-internet days when I was hiking them, but I was not using the internet for research at the time and did not really even know if it was out there.
I really enjoyed the experience of having very little information on routes and finding my own way to the summits solo with a map and compass. That's not to disparage other means of locating the summit (GPS, following a group, etc.), just to point out that I enjoyed NOT knowing the exact routes others had taken and enjoyed having to rely on a combination of map and compass and terrain features.
The part that made the NEHH feel different was the logging slash, the impenetrable spruce whose trunks were sometimes too close together to squeeze between, and the lack of herd paths. Sometimes I found a herd path, but just as often there was no sign of one. I only ran into one other person ever while doing the BW peaks, a man coming up from another direction (Moose Mountain I think but would have to look at notes) We were able to hike out together.
My experience (limited) was that when asking for the information I wanted on the NEHH, I was given it. I also asked for very little information...but enough.
As far as the summit registers were concerned, all I recall seeing was sporadic names, an occasional comment related to peak number on a list, and an occasional drawing. I often draw a raven outline. I never saw a derogatory comment in a register on these summits, but again, I was limited to NEHH BW peaks and other than a handful of TW peaks, most were over 10 years ago. Apparently, things may have changed. Too bad if so.
I am of the opinion that it should take asking for the information personally, but not that it should be a secret. I can see why some of this info is not posted online which might encourage overuse. Maybe it shouldn't be that easy. I can also understand why people who have slaved over maps into the wee hours may not want to give that info up to anyone who asks. We all have the means to calculate these lists ourselves if necessary. The reality is I think most people who had this info would choose not to use it after finding out the reality of bush whacking. It's not the champagne and caviar it's often cracked up to be.