Unfortunately, you are correct about the information available today. Yes, Wullf, Brooks, and others wrote about fly fishing back in the 60's. However, the focussed on how and why not when and where. I remember reading Joe Brooks talking about fishing for Missori River brown trout in the fall. However, he never mentioned where on the Missouri he fished. He did talk about how to dress for cold weather, and what equipment to use and why.
After moving to Montana, I went exploring and found exactly where Brooks was fishing for the large fall browns on the MIssouri. It was an out-of-the-way spot that was not that difficult to get to if you were willing to do some exploring with a 4X4, or willing to walk thr river bank for about 2 miles through a narrow canyon. The fishing was wonderful until the Kokanee Salmon were released into the river from an up stream irrigation diversion dam. The Kokanee spawn ant the same time as the browns and were digging up the brown trout redds. This area is only a ghost of what it used to be. But I digress.
My point is that Joe Brooks never told the exact where or the exact when, neither did Wulff, etc. All Brooks said was fall brown trout fishing on the Missouri River in Montana. Charlie Brooks was the same with his articles and books on the Madison and other Yellowstone waters. Charlie Waterman did the same as well. This despite that Charlie lived in Monatan 6 months/year and new exact where and when on mny Montana waters.
Interestingly, Gary LaFontaine gave when and where except for his two favorite places, the upper Clark Fork River and upper Rock Creek. Waters that I spent many an ejoyable evening or morning on, including having Gary come by and chat before or after fishing. He also never spoke about Flint Creek where I would also run into him at times. However, Gary wrote a lot about the Bighole river and the Missouri River, he claimed is was needed to "preserve" the fishery. Gary guided on both these rivers and had a guide friend in Helena, MT who guided on each of them. Guess who he mentioned in his articles about these two rivers?
I liked Gary and he was a very generous and honest man. However, I wished he would never had publicised the Missouri and Bighole Rivers.
Wulff would say he fished the Yellowstone River, Schiebert would say he fished the Madison river or Firehole River. They never said where they fished them or exactly what time of year.
I sure would like to see some of the same restraint practiced today by the fly fishing scribes. And, like you, I think that part of the answer would be to have state fisheries department limit the number of guides that could work a river, or stretch of river.