Because the cost to OpenAI to make an architectural shift is far greater than the cost to a new lab to try something different, providing details is usually a net benefit for recruiting, building trust, getting acquired, etc. The lack of details is a poor business decision because it makes them seem untrustworthy.
I'm not advocating that they should open source their model, but there is already so much noise in the space and many bad papers that being cagey is a poor strategy for winning over talent, developers, etc.
OpenAI validating it can still happen faster than they can get the compute to serve the models themselves[1]. It doesn't make a lot of sense to give out details if they want to be a serious contender or even as some have said, be acquired.
Yeah there's noise but if they have the real deal then it doesn't matter. They only thing they need to do is let people pay to use the models.
[1] I'm assuming this is the primary cause of the delay. That may not be the case of course.