As an aside, if "familiar interface" is your only requirement, I'd suggest to install a door handle or light switch.
With Windows 10, this problem will likely get a whole lot worse. What do you do when MS pushes a forced update to your deployed devices and it bricks some of them? http://m.theregister.co.uk/2016/05/06/microsoft_update_asus_...
What about when you can't disable Cortana (without breaking the start menu) and you're in a HIPAA / PCI environment? http://winaero.com/blog/how-to-uninstall-and-remove-cortana-...
As we've seen with things like SCADA, switching from Windows is not a silver bullet, but in terms of minimizing the complexity and attack surface, Windows seems to be starting at the opposite end of the spectrum.
However, I do question "it looks like Windows" as a valid rationale for what appears to be a single-purpose machine. I don't think it's likely that staff are using the operating room equipment as a desktop machine, so presumably they only care about the in-app user interface. And an application interface can be made to "look like Windows" regardless of what OS it's running on.
If users are never meant to interact with the OS itself (airport terminals, ATMs, displays, etc.) then it makes absolutely no sense to use Windows.
This isn't far from the truth. You'd be better of providing a console with clearly labelled buttons and switches. No operating system exposed to the user. It's not very practical to implement, let alone make changes to, but it would be more dummy proof than any desktop application.
This is also why you see a lot of kiosk-like, full-screen applications, with no ability to actually work with the desktop interface itself. A single kiosk application that cannot be alt-tabbed out of, providing screens that are easy to navigate.
