The Microsoft Solitaire Pack or whatever the current branding is does, indeed do something behind the scenes to ensure the game is winnable.

I suspect they have either a massive database of proven-winnable shuffles, or before the game presents a new deck to you, it solves it in the background to prove it's winnable.

Personally I dislike this feature. Yeah it sucks to get an unwinnable shuffle, but that's just how card games work. Ensuring every game is winnable just seems like addiction engineering when it's next to the Microsoft logo.

Part of the fun is the uncertainty that a game is possible to win. If you know up front that a deck is guaranteed solvable, it really colors how you play the game.

Part of the mechanism of psychological addiction is unreliable, intermittent rewards. People feel like they are in control but can't figure out the optimal win strategy. One effective means of treating gambling addiction is to just teach people how to get good at gambling. It removes the mystery of the system and puts the subject back in control. So, making every hand winnable may actually help to make the game less addictive.