Okay. Seems Windows 10 should respect that setting and boot to tablet mode. Windows 8 (before the Surface Go, of course) could boot to tablet mode with this setting.
I will list this as a 'bug' in Windows 10 and post what I find out.
Interesting, I have my Surface Pro 6 to automatically enter tablet mode if it does not detect the Type Cover is connected OR the Type Cover is flipped behind the Surface Pro 6 (instead of in front. This basically accomplishes the same thing as it makes the keyboard deactivate).
So if you have "auto tablet mode" enabled and boot up the Surface Pro, it will automatically boot up to Tablet Mode, no? Mine works this way everytime. I may be one of the few I guess...