The proclamation is rather bizarre when you consider that most hardware makers work directly with Microsoft to pre-certify their components to work across a variety of laptops. Now, Sony is one of the few OEMs who does make some electronics modules first-hand, so it's possible it has some oddball parts (think webcams).What's exactly going on remains a bit of a mystery as in a follow up comment, Sony refers to not only the drivers but also to its applications (aka the bloatware). DailyTech goes as far as to speculate that perhaps Windows 10 is now too secure for Sony's obtrusive DRM and that this may be part of the problem.
But that still doesn't answer the question of why Sony is having so much difficulty porting its drivers to Windows 10, particularly when Microsoft Corp. (MSFT) sent out many explicit warnings to hardware makers to remember to sign their drivers. And even if Sony was grossly negligent enough to forget to sign its drivers, most previously certified drivers work just in Windows 10 (and when they don't there's the troubleshooting mode).
Sony claims it will have upgrade instructions available by the end of the month but Windows 10 compatible drivers and applications won't arrive until October/November 2015! But that's only if you have a Windows 8.x laptop, if you have a VAIO laptop with Windows 7 you may be out of luck entirely as Sony doesn't seem to plan to provide Windows 10 compatible software for these older systems.