Actually, it makes quite a bit of sense to release them roughly at the same time, or the OS a little ahead of the associated HW. You don't want to release a HW with the old OS only to have a new OS out a few weeks later. They can also be used to showcase each others strengths.
Maybe they should wait until Windows 10 Update 1 [ I'm dubbing it Win 10.10
], you know as soon as Win 10 hits the OS pundits will say wait for Update 1, and the Hardware pundits will say wait for Firmware update 3. Putting them together is suicide.
This is borne out of Microsoft's project management style of releasing before its done and propensity to follow the 80/20 rule. Seriously, it was time a decade ago for Microsoft to put their big boy pants on and up their game to at least 90/10 and start getting it right the first time at least once in a while.