This is an actual leaked document and the mod at B3D stated it, and it seems quite a few have read it. Its not new.
It was on a number of sites, one below, the document has been since removed off twitter.
Microsoft has still not publicly acknowledged its Lockhart plans
www.theverge.com
Most of the press took from the document the lockart info, not the dev kit issue - I am sure its fixed already, but it is a reasonable explanation for PC only at teh show at this time.
Why do you think mS has not showed XSX running games at the mS show ?