Last night, on my new Windows 10 machine, I received a notification "You got a message on your phone; Want to see phone messages on this PC too?" I've never installed Microsoft's phone app, and there's no way it could possibly know I just got a message. In fact, I didn't just get a message at all, and hadn't for hours.
So, they're lying. They're straight-up, bold-faced, red-handed, lying to their customers to get us to install their spyware which reads and syncs your text messages.
I'm finished with Microsoft. They're such a garbage company and always have been.