What do you mean legally distinct? You know that's Sam Lake, writer and creative director at Remedy, and face model for Max Payne 1/2, both also developed by Remedy?
I know. Rockstar acquired the rights to Max Payne at some point before releasing Max Payne 3. Remedy couldn't just include a character they didn't own, but they couldn't stop Sam Lake being Sam Lake either. Plus Casey being the knock-off of two out-of-universe characters is funny.
Ah, I guess I didn't know they didn't have the rights anymore. Tbh I played through AW2 and didn't connect that Casey was a reference to Max Payne lol.
It's a bit more obvious if you've played through AW1 and Max Payne recently. AW1 contains a couple of excerpts from Wake's book The Sudden Stop, starring detective Alex Casey. They are written in the exact same style as Max Payne, and narrated by James McCaffrey, Payne's VA.