I did a brand new Windows install recently and it had all sorts of icons for apps in the Start Menu that aren't made by Microsoft. Candy Crush, some racing game, some other game, Spotify. In fact, some of these "pre-installed" apps weren't even installed (like crapware is) at all. They were icons that install the apps (or take you to the store) once you click them.
You honestly don't think those are ads? It's Microsoft pushing "install this!" icons for third-party apps from the store in your face in a non-related UI place in the OS, that you have not chosen to install. There is no other proper name for that than an ad. The apps are not even remotely related to Windows as a product and you don't have to even go to the store to see them- they are in a standard OS menu.
To be fair- I don't (as much) mind some Microsoft products being treated this way (OneDrive, Skype), because I would expect the creator of the OS to push their own stuff.
There is zero comparison to the MacOS App Store (where obviously there would be ads for apps... because it's a store... for apps.) If Apple started putting Candy Crush, Racing Games, and Spotify in my Dock on a new install- I would have just as much a problem with that.