Two things. First, many of the guides at iFixit are user generated. A Quality Guide takes time to complete. Even if you know the process by heart, it still means documenting the process step by step. This entails photographing and/or videoing the process. Writing everything out in clear and concise steps and assembling everything together in a way that tells the story of how to perform the repair.
Second. I cannot speak for iFixit, but I don't know that there was mention of documentation being specifically provided as part of the agreement with Valve, only providing parts. I suspect guides will come (user generated or otherwise), but iFixit sells lots of parts that do not have explicit guides for install. And agreements for distribution/sales of that sort also take time to hash out and implement. Apple announced their Self Repair program in November and just rolled it out a few days ago. I know it's not always the easiest thing, but I think in this case, patience is the best antidote.