They also didn't specifically preclude the possibility of commandeering my computer by pushing an update that'll force me to mine bitcoin for them, but I can be pretty damn sure that's not going to happen.
But let me rephrase anyway: I'll bet everything in my pocket that Windows 10 does not, nor will they ever, keylog every stroke and send it back to Microsoft servers for storage.
I can be sure of this the same way I'm sure about many other things I have no definite proof of -- I see nothing remotely resembling evidence that this might take place.