I don't doubt that the Surface Book only runs Windows 10.
But that's not "awful". Windows 10 is a fine OS. I don't personally like it as much as Win 7, but it's perfectly usable. I'm running it now at work and at home and it's okay. Hardly "awful".
You do have to turn off all the stuff that sends your personal data up to Microsoft Central, but it turns out that's pretty easy.
> ...I'm running it now at work and at home...
In virtual machines (VMs). As a learning experience.
In general, I plan to stick with Win 7 until it loses support in 2020, because I prefer its look and feel to that of Win 10.