In any event, during the installation process, you do see a screen where you can turn all this off. It's not off by default, but viewing these settings was part of my Windows 10 installation experience.
The problem is that Windows 10 does not respect you having this turned off. It will send away your data, even if you turned off all the switches.
Don't you see this as a huge problem?
Otherwise wouldn't every commonly misspelled word show up incorrectly in spellcheck?
There is quite a bit of work in the field of speech recognition, too, and it's entirely possible to create a functional model without recording every user's voice and storing that information on a server. Even if they require speech samples, or samples from different languages, they should at least pay someone for that information.
I was disappointed when I learned that the voice recognition feature in Siri wasn't local to the phone.
Do you know what actual data is, and is not, sent to Microsoft as you use your device?
Even if you do, will you still know once Microsoft pushes a mandatory update and/or changes its 12,000 word terms of service?