Unknown Soldier
Veteran
PCGamer has it as Virtuous hence why I used it.It's not well advertised. A quick google search of Virtuous & Horizon Zero Dawn doesn't even turn up anything.
As already mentioned, communication was with Guerrilla, so why would they think it was anyone else unless they were explicitly told?
edit:
There's a single mention here:
https://www.pcgamer.com/horizon-zero-dawn-pc-performance-benchmarks/
Apparently, it's actually spelled Virtuos
https://mobilesyrup.com/2020/08/05/horizon-zero-dawn-pc-port-review/
And the HZD wiki page doesn't even mention them, nor does the Virtuos page mention the port.
Virtuous, the developer behind the port, on behalf of Guerrilla Games
https://www.pcgamer.com/horizon-zero-dawn-pc-performance-benchmarks/