They want to sell more devices by improving security and having official support for GrapheneOS. The main work that's being done is official GrapheneOS support.

They want to sell more devices by improving security and having official support for GrapheneOS. The main work that's being done is official GrapheneOS support. They're also going to integrate improvements from it into their own OS but that's not the main focus. They may not want to do as much integration into their own OS if it was all GPL but it's a side benefit for them rather than the main purpose.