I don't know about official releases of documents, but there are a lot of vintage documents on bitsavers.org.

IBM has a very long history of diligent notetaking, maintaining several journals dedicated to internal development stretching back into the 50's. While I certainly haven't read everything, I've read enough to feel comfortable saying that the quality has had a sharp decline as transparent marketing replaced useful engineering. I suspect I'm not the only one who felt that way, because they recently shuttered those operations and tragically handed everything (from what I can tell) over to the paywalls. I generally don't feel much one way or the other about corporations, but seeing IBM decay like this genuinely makes me gloomy.

https://sci-hub.se/10.1109/4.45001 https://sci-hub.se/10.1147/rd.342.0416 https://sci-hub.se/10.1147/rd.342.0428