Hi,
The disability section isn't viewed by the general administration team it means that the disability services will contact you to set up support rather than you having to send the first email.
When I was doing the process I put working diagnosis of autism and the uni contacted me about the support they could provide but also what a formal diagnosis letter would provide extra support
By the time I had started at uni I had the diagnosis. As you won't be setting up the support until nearly September then you should have the paperwork before hand