You are likely referring to the save game data being exclusive to a particular platform for Forza Horizon 1.
The game typically checks for these saves the first time you play. If you play the older games later, you may need to restart your Horizon progress or trigger a re-scan to receive the cars according to Forza Wiki . forza horizon 1 save game exclusive
Example: a promo pack might add the “2010 Lamborghini Estoque” as a bonus car — the save records ownership of that car once redeemed. You are likely referring to the save game
To "save" the file and unlock the cars for his own profile, Leo has to beat the Ghost of Darius Flynt in a midnight downhill sprint. The catch? If he loses, the save file deletes itself forever, erasing the legacy of the original player. Example: a promo pack might add the “2010
Awarded if you reached any level in FM3. Forza Motorsport 4 Profile: 2011 Ford F-150 SVT Raptor: Awarded for reaching Level 1. 2010 Bugatti Veyron 16.4: Awarded for reaching Level 5.
If you want, I can: