Yes. Also Xbox players would get the the reward from playing FH4 on Steam. Also, if you play on Steam and on Xbox, you'll get the rewards in both games.
These are one-time gifts given after you complete the first Horizon Story chapter (about 20 minutes into the game). Note that the rewards are based on your history at the time you start FH5; if you play an older game after starting FH5, that reward won't be added retroactively. But don't worry if you miss any of these cars, since they're not exclusive and you can pick them up through regular gameplay.
- Played FH1: 2013 DODGE SRT VIPER GTS
- Played FH2: 2014 LAMBORGHINI HURACÁN LP 610-4
- Played FH3: 2016 LAMBORGHINI CENTENARIO LP 770-4
- Played FH4: 2018 McLAREN SENNA
- Played FM5: 2013 McLAREN P1
- Played FM6: 2017 FORD GT
- Played FM7: 2018 PORSCHE 911 GT2 RS