Based on what we have seen so far, its not exactly a lot of work to update from 5e to 1D&D. It only takes a few minutes to update a subclass from 5E to 1D&D. A developer could wait until the new rules are almost out to start working on new products, or they could start working on products now and update them before 1D&D is release. I mean, I guess starting products early is technically more work, but it also gives you a year of extra time to work on more products. Game developers tend to have more than one idea. They could easily have 10 times the products available for the launch of 1D&D.
I don't mean to be insulting here, but this seems like a strange point to get hung up on. Is there actually any disadvantage to explaining the terms of the new OGL? Why not release the info as early as possible? As a general rule ,I think being as open and honest as possible is a good thing.