Windows 10 advantages (DX12) are a little situation, Ashes clearly seems to benefit but the likes of most games made for console and ported are not CPU or GPU bottlenecked on a half decent rig.
I would be very careful not to leave an impression Ashes of a Singlelarity can only be played well on Windows 10. Although Supreme Commander (including FA) were in my opinion the best RTS games of all time, the sales were relatively poor due hardware requirements of the day AND the perceived hardware requirements of the day. Many people had PC's that could run Supcom on mid range PC's if they stuck to medium and small maps, buts that message failed to get through, there are lessons to learn imo.
Some people are just stubborn with wanting to upgrade away from Windows 7 (think they are nuts myself), remembering the utter hunk of junk that was Win8, Stardock probably doesn't want to isolate these people.
Not being able to dual monitor Supcom FA on Windows 10 ATM is kinda annoying!, seems I need a new game