Yeah, when you own Hitman 1/2 it then gives you access to an additional piece of "DLC" that is basically a DLC for Hitman 3 that tells the game to give you the levels from 1/2.
The nice thing about this system is when Hitman 2 was on PS Now for the week after Hitman 3 launched you could use that access to create the Hitman 2 access DLC for Hitman 3, and now I have Hitman 2 access within Hitman 3 even though Hitman 2 isn't on Now anymore.