I think they have a communication problem anyway. And it's not just their headquarters but it's also regional issue. 30th Anniversary devices pre-orders were a disaster in my country. They said 'we will have further announcement' and then went silent. We didn't had opportunity to order Pro 30th and no one said anything about that. People were waiting days after. I assume that in the end they'll make some competitions with few Pro 30th as prizes. Maybe. 20th Anniversary was bad but at least we had some chances of getting it.
As you wrote, no one was expecting that the Slim console, which should be smaller then Standard, will have compatible plates. This time, because of the design and the drive compatibility, we can be expecting that.
It should be stated at least in the blog post or some Q&A by Sony. It's basic stuff. Maybe Sony doesn't know

.
Maybe we will know after watching teardown, if there will be any…