Forza Horizon 3, Microsoft Store and Windows 10 built in store differ?

The Microsoft Store offer is only for purchases through the Microsoft Store, which is different from purchasing through the Windows 10 Store. Usually Microsoft Store purchases are only physical copies of the game, which may have been eligible for a $10 discount
on future purchases from the Microsoft Store, but this is separate from the digital-only Windows 10 Store.

Hope this helps clarify things.

Hi there NIGHTRIDER!

Based on the info listed under "Capabilities" on the
Forza Horizon 3 Store Page , cross-platform play between Windows 10 and Xbox consoles is supported, yes

Open the Windows 10 Microsoft Store app > Make a left-click on the 3 consecutive dots (Top Right) > Select My Library > Once you're there you should see Forza Horizon 3. You will need to sign in to the Store with the same Microsoft account that you purchased
the game on your Xbox.

Hi! You can pre-order Forza Horizon 3 here:
www.microsoft.com/.../bpwf8jk5sq4m

Since it supports Xbox Play Anywhere, you can play the game on Windows 10 and Xbox One as long as you buy the digital version on the store.

I have a theory

I think it's because Microsoft haven't added a forza 3 plus the hot wheels package to the windows store or the Xbox store so it can't recognise what we have bought. I've just been on the windows 10 store and checked every version of the game but they all
ask me to pay money. If I go on the 3 dots on the top right of the windows store and choose purchased its right there on the list but it says forza horizon 3 and hot wheels expansion bundle. Something that is not on any store.

Microsoft can you please add it. I sold my playstation to buy this Xbox. Don't make me regret it.