Solo or small dev teams may not have resources to support both desktop/laptop & mobile. If I understand correctly, this may give GrapheneOS users access to some desktop/laptop only apps when desktop/laptop not available.
Discussion
that there has to be seperate OS's for mobile than desktop just shows how far open source has yet to go in the future...but yea...it's definitely a big divider when coding something new....what hardware target market are you aiming for is a pretty big split right at the start.