People who are fixating only on PC ports are uninformed. Nixxes is so much more than that. They refer to themselves as a "Video Game Co-Development" company.
This is what they do.
In addition to the four bullet points, they also build new console technologies (hardware and software). They created new technologies for both PS4 Pro and Xbox One X. And one of their bigger goals is to increase the efficiency and optimization of games and build technologies around that goal. Basically, they will also be helping PlayStation Studios get better performance out of PS5.
Their role in the PlayStation Studios Head Forum would be crucial and priceless.
Edit: Forgot that they also work on
Game Engine development. So expect lots of core game engines improvements across all studios in the PlayStation Studios family.
Apart from providing active game-development support, expect them to assist ICE in improving technologies across PlayStation Studios.